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Interstate 55

Interstate 55 (I-55) is a major north-south spanning 964 miles (1,552 km) in the , connecting the Gulf Coast to the Midwest. It begins at an interchange with (I-10) in , and ends at (US 41) near downtown , , passing through , , , , , and . The route primarily follows a path parallel to the , facilitating commerce and travel between key metropolitan areas such as New Orleans, , , , and . Designated as part of the National System of Interstate and Defense Highways, I-55 was established in 1957 and fully completed by the early 1970s, with sections opening progressively from the 1950s onward. It serves as a critical component of the National Highway System, carrying significant freight traffic as one of the primary corridors linking southern ports to northern industrial centers. The highway intersects major routes including I-12 in , I-20 and I-40 near Jackson and , I-57 in , and I-90/I-94 in , enhancing regional connectivity. Throughout its length, I-55 traverses diverse landscapes, from bayous and rural farmlands in the to urban expanses in the North, with notable features like the over the at and the Stevenson Expressway designation in the area. Ongoing improvements, such as lane expansions and bridge rehabilitations, address growing traffic demands and safety concerns, particularly in high-volume sections around and .

Route description

Louisiana

Interstate 55 enters at its southern terminus, an interchange with in LaPlace, St. John the Baptist Parish, about 25 miles west of New Orleans. From there, the four-lane freeway heads due north through low-lying wetlands and timberland, paralleling U.S. Route 51. The initial segment features a series of elevated s over swampy terrain, including the 5.5-mile-long viaduct system at Ruddock that spans canal crossings and flood-prone areas. North of Ruddock, I-55 transitions onto the 22.8-mile , a twin trestle constructed in 1979 that carries the highway over the expansive Manchac Swamp between to the east and to the west. This structure, one of the longest toll-free bridges in the world, elevates the route approximately 25 feet above the marshy ecosystem, minimizing environmental impact while providing a direct path. The bridge ends near the Tangipahoa Parish line, after which the highway descends to grade level and passes through Ponchatoula, a small city known for its strawberry production. In Hammond, the largest city along the route, I-55 intersects —a key east-west corridor linking Baton Rouge and Slidell—and , facilitating access to local businesses and . Beyond Hammond, the freeway continues northward through rural Tangipahoa and St. Helena parishes, bypassing Amite City and serving Kentwood with exits for local roads. The Louisiana segment concludes at the Mississippi state line north of Kentwood, after a total length of 65.81 miles, primarily functioning as a commuter and evacuation route for the .

Mississippi

Interstate 55 enters from in rural Pike County near Osyka, marking the southern terminus of its 290.41-mile (467.37 km) journey through the state. The highway initially traverses densely forested timberlands in southwest , providing a vital link between the Gulf Coast region and the state's interior. It serves as the primary north-south corridor, largely paralleling the older and facilitating commerce, tourism, and daily commuting across rural and urban areas alike. Northbound from the state line, I-55 quickly reaches McComb in Pike County, a regional hub where it intersects , offering access to local industries and services. The route continues through Lincoln County to Brookhaven, crossing and passing near agricultural lands and small communities. As it approaches the state , the highway enters Hinds County and expands to six lanes in the Jackson , handling heavy traffic volumes. In Jackson, I-55 forms a significant overlap with , crossing the and intersecting , which provides eastward connections to Hattiesburg and westward to Vicksburg. Additionally, Interstate 220 branches northwest from this junction, serving as a bypass around downtown Jackson. Leaving Jackson, I-55 resumes its northerly path through affluent suburbs like Ridgeland and in Madison County, where it remains a six-lane freeway amid commercial developments and office parks. The route then transitions to four lanes as it passes , intersecting Mississippi Highway 22 and entering more rural terrain in Holmes and Attala Counties. Further north, it reaches in Grenada County, crossing Mississippi Highway 8 near Grenada Lake, a popular recreational area. Continuing through Yalobusha and Panola Counties, I-55 serves Batesville with access via Mississippi Highway 6 and then approaches Tate County, passing Senatobia. In the northernmost segment, I-55 enters DeSoto County, intersecting near Hernando and overlapping with the future for approximately 9.2 miles toward the state line, with widening projects adding lanes to accommodate suburban expansion in Hernando and Southaven. The highway exits near Southaven, crossing into and providing seamless access to across the . Throughout its length in the state, I-55 features modern rest areas, crossings in rural stretches, and ongoing improvements for safety and capacity, underscoring its role as a backbone of Mississippi's transportation network.

Tennessee

Interstate 55 traverses the state of entirely within Shelby County and the city of , spanning approximately 13 miles from the state line to the state line. Entering from , the highway proceeds north through southern , initially paralleling the state line before curving eastward slightly. It serves as a key north-south corridor for local and through traffic in the , facilitating connections to regional commerce and transportation hubs. The route's first major interchange occurs with U.S. Route 51 (Elvis Presley Boulevard) near the southern edge of the city, providing access to residential and commercial districts. Proceeding northward, I-55 intersects Interstate 240 at a partial cloverleaf interchange adjacent to Elvis Presley Boulevard, allowing seamless transfers to the Memphis beltway for routes to downtown, the east side of the city, and Interstate 40. North of this junction, the freeway passes immediately west of Memphis International Airport, offering indirect access to the facility via connecting roads and I-240 while avoiding direct airport congestion. Further north, I-55 encounters an interchange with U.S. Routes 61, 64, 70, 78, and 79 (South Parkway East), serving industrial and urban areas in south . The highway then veers westward toward the , reaching the complex interchange with Boulevard and South Riverside Drive. Here, I-55 crosses the river on the , a nearly 76-year-old cantilever truss structure built in 1949 that is planned for replacement by the Kings' Crossing bridge with construction starting in 2026, before entering . This segment handles high volumes of commuter, freight, and tourist traffic, with ongoing improvements addressing congestion and safety concerns.

Arkansas

Interstate 55 enters Arkansas from Tennessee via the Memphis & Arkansas Bridge, a cantilever truss structure spanning the Mississippi River into West Memphis in Crittenden County. Upon entering the state, I-55 joins a brief 3.1-mile (5.0 km) concurrency with Interstate 40 through downtown West Memphis, providing essential connectivity for the Memphis metropolitan area and serving heavy freight traffic along the river corridor. North of the I-40 split at exit 1, I-55 proceeds northward as a four-lane divided freeway through urban and suburban sections of West Memphis, with exits providing access to Arkansas Highway 77 (exit 5), U.S. Highways 70 and 79 (exit 7), and the town of Marion (exit 8). The route then transitions into more rural terrain in northern Crittenden County, intersecting U.S. Highway 64 near Earle (exit 10) and Arkansas Highway 77 again (exit 12), before reaching Turrell at exit 21. At exit 23 near Turrell, I-55 meets the southern terminus of Interstate 555 and U.S. Highway 63, a key link to Jonesboro approximately 45 miles northwest, providing access near Earle. Continuing north into Cross County, the highway passes near the small communities of Gilmore and Tyronza, with interchanges at Arkansas Highways 42 (exit 26), Arkansas Highway 14 near Sunset (exit 34), and Arkansas Highway 181 near Bassett (exit 36). The route remains predominantly rural, characterized by flat agricultural lands of the , paralleling U.S. Route 61 to the west and the . In Poinsett and counties, I-55 offers exits to Arkansas Highway 463 near Tyronza (exit 31), Arkansas Highway 77 near Lake City (exit 42 and 60), Arkansas Highway 140 near (exit 48, serving area near Lepanto), Arkansas Highway 238 near (exit 53), and Arkansas Highway 325 near Monette (exit 57). Approaching the northern state line, I-55 serves the city of Blytheville in Mississippi County, a regional hub for manufacturing and agriculture, via interchanges with U.S. Highway 61 (exit 63) and Arkansas Highway 18 (exit 67), the latter providing access to Blytheville and nearby Eaker Air Force Base remnants. The highway then intersects Arkansas Highway 181 one final time at exit 71 before crossing into near Gosnell, completing its 72-mile traversal through northeast as a vital north-south for , , and regional travel. Throughout its path, I-55 functions as a National Freight Highway, supporting moderate to heavy truck volumes and connections including I rail lines parallel to the route.

Missouri

Interstate 55 enters Missouri from Arkansas in Pemiscot County near Cooter and travels approximately 209 miles north-northwest through the Missouri Bootheel and along the Mississippi River to St. Louis, where it crosses the Poplar Street Bridge into Illinois. The route primarily parallels U.S. Route 61 and serves as a vital corridor for freight and passenger traffic, connecting rural agricultural areas in the southeast to the urban St. Louis metropolitan area, with rest areas at mile markers 21 (near Hayti), 42 (near Marston), 110 (near Jackson), and 160 (near Bloomsdale). From the Arkansas state line, I-55 proceeds north through flat, low-lying farmland in the Bootheel region, passing near Hayti (mile marker 15) and Portageville (mile marker 31) with interchanges for local routes. It continues to New Madrid (mile marker 57), where it intersects Missouri Route , and then reaches Sikeston (mile marker 66), a key junction with U.S. Route 60 and the northern terminus of , facilitating connections to and beyond. North of Sikeston, the highway traverses Scott County, offering access to Morley (mile marker 72) and (mile marker 80) via local roads amid and fields. Entering Cape Girardeau County, I-55 shifts to slightly rolling terrain as it approaches Cape Girardeau (mile marker 99), providing multiple exits including Route 74 (mile marker 95) leading to the Emerson Memorial Bridge across the to . The route then passes through Scott City (mile marker 91) and continues northwest into Perry County, serving Perryville (mile marker 119) with an interchange at U.S. Route 61, the primary parallel highway. In Ste. Genevieve County, the freeway reaches Bloomsdale (mile marker 147) and crosses into Jefferson County near (mile marker 174), where it merges with for a concurrency northward, with ongoing lane expansion and bridge rehabilitation projects in the Jefferson County corridor addressing growing traffic and safety needs. In the St. Louis suburbs, I-55 expands from four to six lanes near Pevely (mile marker 185) and further to eight lanes at Barnhart (mile marker 187), accommodating increasing urban traffic volumes. It crosses the —Mingo and Big Creeks before entering St. Louis County over the near (mile marker 189), then interchanges with Interstate 270 (mile marker 199), a beltway encircling the metro area. Within St. Louis, the route narrows to six lanes through densely developed areas, overlapping briefly with (1 mile) near the and intersecting / (0.4 miles) downtown before ascending to the Poplar Street Bridge, a multi-level structure carrying I-55, I-64, I-70, and U.S. Route 40 across the .

Illinois

Interstate 55 enters from across the Poplar Street Bridge over the , reaching East St. Louis in St. Clair County. Upon entry, it joins a short concurrency with and for approximately two miles, after which I-64 departs eastward while I-55 briefly overlaps with near the . The highway then proceeds northeast independently through the area, serving Collinsville and Edwardsville in Madison County before entering more rural terrain in Macoupin and Montgomery counties. It passes through smaller communities such as Livingston, Worden, and Staunton, reaching Litchfield as it transitions toward . In the central portion of the state, I-55 continues northeast through Sangamon County to the capital city of , where it overlaps with for about seven miles from the southwest side to the northeast. Departing , the route heads north through County to , then enters County and the Bloomington-Normal metropolitan area. Here, I-55 overlaps with Interstate 74 for roughly 13 miles while intersecting at a major junction that facilitates travel toward Rockford and points north. Beyond Bloomington-Normal, the highway maintains a predominantly rural character, traversing DeWitt, , and Livingston counties and passing through towns like , , and before reaching Dwight in Grundy County. Entering Will County, I-55 intersects Interstate 80 near Channahon and Joliet, providing access to the expanding southwestern suburbs. North of this interchange, the route shifts to an urban profile as the , crossing into DuPage and counties while serving Lockport, Lemont, Darien, Burr Ridge, and other communities. It parallels the and the and Michigan Canal in places, intersecting (Veterans Memorial Tollway) and (Tri-State Tollway) before reaching the ( 90 and 94) in . The highway terminates at a partial interchange with () adjacent to and the shore of . Throughout , I-55 functions as a vital north-south corridor linking St. Louis-area commerce with the metropolitan region, carrying significant freight and commuter traffic.

History

Planning and approval

The development of Interstate 55 formed part of the broader planning for the National System of Interstate and Defense Highways, first authorized under the Federal-Aid Highway Act of 1944, which envisioned a 40,000-mile network to connect principal metropolitan areas, cities, and industrial centers for national defense and commerce. Detailed route alignments, including the primary corridor for what would become I-55 from the Gulf Coast region northward through the Mississippi Valley to , were outlined in the Bureau of Public Roads' September 1955 publication General Location of National System of Interstate Highways, Including All Additional Routes at Urban Areas Designated in September 1955—commonly known as the "Yellow Book"—which mapped approximately 37,000 miles of rural interstates and 4,000 miles of urban connections based on extensive state consultations and traffic studies conducted since the late 1940s. Funding and construction authority were secured through the , signed by President on June 29, 1956, which expanded the system to 41,000 miles, allocated $25 billion over 13 years via the newly created financed by increased gasoline taxes, and mandated 90% federal funding for right-of-way acquisition and construction while requiring states to approve routes and handle local planning. This legislation marked the formal approval for proceeding with projects like I-55, emphasizing controlled-access design, minimum standards for width and curvature, and integration with existing highways such as in the South and in the North. Route numbering, including the assignment of I-55 as an odd-numbered north-south (with the last digit 5 indicating a route from the Canadian border area southward), was finalized and approved by the American Association of State Officials (AASHO, predecessor to AASHTO) in collaboration with the Bureau of Public Roads on September 20, 1957, following a grid-based scheme where numbers increased eastward for north-south routes to avoid overlap with U.S. numbers. State-level approvals and initial studies commenced shortly thereafter, with the first federal-aid construction contract for I-55 advertised in in late for a 27-mile segment from the state line southward, reflecting early prioritization in the region for economic connectivity. In Illinois, planning for the northern urban segment through Chicago dated to 1927, when the Chicago Plan Commission proposed a radial expressway system utilizing the right-of-way of the abandoned for a southwest corridor to alleviate congestion on ; this alignment was reaffirmed in the and received state approval in the mid- as the Southwest Expressway, later designated I-55. Similar state planning in , , , , and involved corridor studies in the early 1950s to link New Orleans-area ports with Midwestern industrial hubs, with federal approval contingent on environmental and right-of-way clearances under the act's guidelines. Overall, I-55's approval process highlighted the system's emphasis on interstate commerce, with the route's 964-mile length approved in phases as states submitted detailed plans to the Bureau of Public Roads by 1958.

Construction

Construction of Interstate 55 commenced in the late 1950s as part of the broader established by the [Federal-Aid Highway Act of 1956](/page/Federal-Aid Highway Act of 1956), which provided federal funding for a network of controlled-access highways to enhance national defense and commerce. The route's development prioritized connecting the Gulf Coast to the Midwest, with initial segments focusing on rural and urban links through , , , , , and . Early approvals targeted high-traffic corridors paralleling , with contracts awarded progressively to address engineering challenges such as swampy terrain, river crossings, and urban integration. By the early 1960s, significant progress had been made, with numerous segments under construction across the route, though completion varied by state due to local funding, land acquisition, and environmental factors. In , began with the elevated bypass of Ponchatoula and Hammond in 1960, providing the first two-lane segment along U.S. 51 from Exits 23 to 28. Further progress included the completion of the route from Arcola to the state line by late , while southern elevated sections south of Ponchatoula expanded to four lanes by 1977. The most complex phase involved traversing the Manchac Swamp, where planning started around 1970 with a fixed-span bridge over Pass Manchac parallel to the old railroad alignment; dredging a along the right-of-way facilitated of this environmentally sensitive elevated roadway. These efforts culminated in the full 66-mile portion by the late 1970s, incorporating twin spans over to link with I-10 in LaPlace. Mississippi's segment saw the earliest approvals, with the first 27-mile portion through Hernando, Coldwater, and Senatobia contracted in late 1956 and groundbreaking in July 1957. By 1963, key sections near McComb, from Crystal Springs to Jackson, and north of Batesville were operational, reflecting rapid rural progress. Urban challenges delayed the Jackson bypass until 1971, while the final 50-mile stretch from MS 16 north of Canton to Vaiden (Exits 124-174) opened in 1973, marking statewide completion of the 290-mile route. Overall, Mississippi prioritized four-lane construction with full control of access, integrating interchanges for local highways like U.S. 49 and I-20. In , the 12-mile urban segment through utilized the existing Memphis-Arkansas Memorial Bridge, completed in 1949 as a four-lane structure carrying I-55 and U.S. 61 across the . The remainder, including connections to I-240 and I-69, was built between 1958 and 1967, making I-55 the first fully completed mainline Interstate in the state. Arkansas's 32-mile portion, linking the Tennessee bridge to the line, followed suit with segments opening in the early 1960s, leveraging preexisting alignments near West Memphis and Blytheville for quick integration into the system. Missouri advanced construction northward, opening an 8-mile stretch from north of New Madrid (Exit 49) to U.S. 60 in Sikeston on September 1, 1960, connecting to an existing 7-mile highway. The route reached by 1967, including the Poplar Street Bridge complex over the , though the final link between Cape Girardeau and poured its last concrete in July 1972. In , the southern extension paralleled historic , with the Stevenson Expressway (originally Southwest Expressway) opening 37 miles from Ogden Avenue to near Joliet on September 1, 1964, and renamed for Adlai E. Stevenson in 1965. Extensions reached by 1966 and completed the Dwight bypass in 1980, finalizing the 313-mile segment amid urban expansions like the 2002-2004 Veterans Parkway interchange rebuild in Bloomington.

Completion and later developments

The final segment of Interstate 55, consisting of the 22.8-mile (36.7 km) in southeastern , was completed and opened to traffic in 1979, marking the full realization of the 964-mile (1,552 km) route from , to , . This twin trestle structure, carrying both I-55 and across the swamp, was constructed at a cost of approximately $7 million per mile (equivalent to $24.3 million in 2023 dollars) due to challenging environmental conditions, including piles driven up to 250 feet (76 m) into the subsurface. Prior to this, most sections had been finished by the mid-1970s, with the last major gap in closed in 1973. In the decades following completion, Interstate 55 has seen extensive reconstruction and widening to accommodate increased traffic volumes, particularly in urban corridors. In , the route's four-lane section through , built in the late 1960s, was supplemented by widening north and south of the city to six lanes during the 1980s and 1990s to alleviate congestion; more recent efforts under the Rebuild Illinois capital program (2019–2025) have included over $1 billion in investments for bridge replacements, interchange reconstructions (such as the $93.5 million I-55/ 59 project completed in 2024), and pavement rehabilitation along the 313-mile segment. Similarly, in , a 12-mile design-build project in County, initiated in 2024 and slated for completion in 2026, adds a third lane in each direction between Pevely and the / county line to improve capacity and safety. Major bridge replacements have also been prioritized to address aging infrastructure. The Memphis & Arkansas Bridge, carrying I-55 across the Mississippi River between Memphis, Tennessee, and West Memphis, Arkansas—originally completed in 1949— is undergoing a $787.5 million replacement project, with design underway and construction expected to begin in fiscal year 2026; the new structure, named Kings' Crossing in 2025, will enhance seismic resilience and traffic flow. In Mississippi, ongoing initiatives include the reconstruction of I-55 from U.S. 49 to I-20/55 in Jackson (estimated completion 2028) and electrical upgrades to lighting systems in Hinds County, reflecting broader efforts to maintain the route's structural integrity amid rising freight and commuter demands. These developments underscore I-55's role as a critical north-south artery for commerce, with annual average daily traffic exceeding 100,000 vehicles in key sections.

Detailed route information

Exit list

Interstate 55 employs a mileage-based numbering in each state, beginning at milepost 0 at the state's southern for northbound travel and increasing sequentially northward within the state. This facilitates , with exit numbers corresponding directly to the nearest state mile marker along the route. Note that mile markers and exit numbers reset at state lines. Minor variations occur at complex urban interchanges, where letter suffixes (e.g., 15A, 15B) denote directional ramps. Rest areas, welcome centers, and weigh stations are typically unnumbered but located near key exits for traveler convenience. The highway features over 250 exits in total, with density increasing in urban areas like Jackson, , , , and . Major interchanges connect to other Interstates and U.S. highways, serving as gateways to regional , , and centers. The tables below highlight representative major exits by state, focusing on significant interchanges, urban access points, and service facilities that illustrate the route's and scale. Mileposts are state-specific. Comprehensive logs are maintained by state departments of transportation for detailed planning.

Louisiana

I-55 spans 66 miles in Louisiana, with 20 exits primarily serving rural parishes and the Hammond area. Exits are spaced 2–5 miles apart, emphasizing agricultural and recreational access.
ExitMilepostLocationDestinations/Notes
10.5LaPlaceI-10 east to New Orleans; US 51 south to Laplace (southern terminus interchange)
77.0RuddockLocal access to communities; fishing areas nearby
2626.0Springfield/PonchatoulaLA 22; entry to Tickfaw State Park
29A/B29.0HammondI-12 east to Slidell; I-12 west to Baton Rouge ()
3131.0HammondUS 190 (business route); downtown Hammond and
5757.0KentwoodLA 21; local services and proximity to border
6161.0State lineLA 38 to Kentwood; final Louisiana exit before

Mississippi

Covering 290 miles, I-55 in Mississippi has about 90 exits, transitioning from forested rural sections to the urban Jackson metropolitan area. Key interchanges support freight and passenger traffic to . Ongoing improvements include bridge rehabilitations as of 2025.
ExitMilepostLocationDestinations/Notes
15A/B15.0McCombUS 98 east to ; local rail and timber industry access
7272.0BrookhavenUS 51 (business); historic downtown and medical facilities
8888.0HazlehurstUS 49 south to Jackson; Copiah County services
92A/B92.0JacksonI-20 east to ; I-20 west to Vicksburg (major eastern junction)
102A/B102.0JacksonI-220 north to I-55 north (beltway start); urban distributor
124124.0MS 16; last segment completed in 1973, rural welcome center nearby
174174.0VaidenMS 35; final rural completion in 1980s
246246.0HernandoI-269 east to I-55 north (future loop); Memphis suburbs
278A/B278.0SouthavenI-269 west to Southaven; casino and retail access
291291.0State lineChurch Road to ; Tennessee border

Tennessee

I-55's 12-mile segment in is the shortest, with 6 exits concentrated in . It serves as a critical link across the , handling heavy truck traffic. The Crump Boulevard interchange (Exit 6) is ongoing as of 2025 for improved .
ExitMilepostLocationDestinations/Notes
10.0I-69 south (future extension); bridge approach
21.5Riverside Drive; overlook and port access
5A/B5.0I-240 east to Nashville; I-240 west to Little Rock (loop interchange)
6A/B6.0I-69 north/US 51; Crump Boulevard ongoing for
77.0US 61; approach to
712.0State lineI-40 west to West Memphis; crossing

Arkansas

The 72-mile Arkansas portion has 22 exits, linking to the via flat delta farmland. Exits support and I-40 connectivity.
ExitMilepostLocationDestinations/Notes
10.5West MemphisI-40 east to ; truck plaza and welcome center
52.0West MemphisI-40 west to ; major east-west junction ()
107.0US 64/US 79 to ; local communities
2315.0TurrellAR 77; access to I-555 north to Jonesboro
3426.0TyronzaAR 118; rural farming services
4234.0GilmoreUS 63; and weigh station nearby
6052.0BlythevilleI-555 south to Turrell; access
6759.0AR 18; Eaker Air Force Base historic site
7163.0State lineUS 61 north; border

Missouri

I-55 traverses 210 miles in Missouri with 74 exits, passing through the Bootheel lowlands to the urban corridor. It parallels the in parts, with frequent US 61 overlaps.
ExitMilepostLocationDestinations/Notes
00.0US 61 south; Bootheel agriculture (unnumbered or first access)
1414.0CaruthersvilleMO 84; ferry nearby, weigh station
2727.0PortagevilleMO A; Crowley Ridge Parkway access
6767.0SikestonUS 62; and rail hub
93A/B93.0Cape GirardeauUS 61; I-57 south to (regional airport interchange)
105105.0JacksonUS 61 north; Cape Girardeau
129129.0PerryvilleMO 51; tourism
170170.0US 61; industrial corridor
174A/B174.0Crystal CityUS 67 north to Farmington; US 67 south to Poplar Bluff
199199.0US 50/US 61/US 67; Lindbergh Boulevard, major metro entry
205A/B205.0I-270 east to ; I-270 west to Chesterfield (beltway)
209210.0State linePoplar Street Bridge to East St. Louis; border

Illinois

The longest segment at 313 miles, I-55 in Illinois features 110 exits, evolving from industrial riverfront to farmland and Chicago suburbs. It is cosigned as the Stevenson Expressway in urban sections. Mileposts are state-specific, starting at 0 at the Missouri line.
ExitMilepostLocationDestinations/Notes
22.0East St. LouisIL 3; Casino and riverfront access
66.0CahokiaIL 111; historic village
1515.0CollinsvilleIL 159; Route 66 heritage sites
3030.0TroyIL 4; Edwardsville University area
5151.0LitchfieldI-55A (former alignment); Chautauqua Parkway
98A/B98.0SpringfieldI-72 east to Decatur; state capitol interchange
109109.0LincolnUS 30; Logan County services
135135.0BloomingtonI-74 east to Champaign; Illinois State University
163163.0DwightI-80 east to Joliet; nuclear power plant proximity
238238.0PlainfieldUS 30; Will County growth area
267A/B267.0ChicagoI-294 north (Tri-State Tollway); O'Hare Airport access
285285.0ChicagoI-90/I-94 (Dan Ryan Expressway); downtown connector
292A/B292.0ChicagoLake Shore Drive/US 41; McCormick Place terminus (northern end)

Auxiliary and business routes

Interstate 55 has several auxiliary Interstate Highways, which are three-digit routes designed to supplement the parent route by providing circumferential, radial, or connecting service. These include I-155, I-255, I-355, and I-555, spanning portions of , , , and . I-155 serves as an east-west connector in the and northwestern , extending 26.77 miles from its western terminus at I-55 near , to an eastern terminus at (future I-69) near . The route overlays U.S. Route 412 throughout its length and crosses the via the Cottonwood Point Twin Bridges, one of only three such crossings in . Construction of the Caruthersville Bridge portion opened in 1971, with the full route completed by November 1979; the western approach was upgraded to expressway standards by July 2007. The easternmost 5.4 miles will eventually become part of I-69. I-255 functions as a partial beltway around the St. Louis metropolitan area, measuring 30.82 miles from its southern junction with I-55 and I-270 in Mehlville, Missouri, to its northern end at I-55 and I-70 near . It provides an eastern bypass for I-55 traffic avoiding , passing through industrial areas and crossing the on the Jefferson Barracks Bridge. The route includes overlaps with and serves as a key commuter corridor, connecting to I-64 and I-270 to form a larger loop around the region. In the Chicago suburbs, I-355, known as the Veterans Tollway, spans 36.53 miles as a from I-80 near New Lenox to I-290 in Itasca, intersecting I-55 near Bolingbrook. This north-south auxiliary route supports radial access to the western and southwestern suburbs, facilitating travel between the southern I-55 corridor and the northwest suburbs while bypassing congestion in central . It features a complex interchange with I-55, including high-speed ramps, and connects to I-88 and I-294. The tollway was completed in phases, with the full Interstate designation approved in the . I-555 in northeastern extends 49.57 miles northwest from I-55 in Turrell to in Jonesboro, largely overlaying as a freeway. Designated as an auxiliary route in 2016, it enhances connectivity between the I-55 corridor and the Jonesboro area, serving agricultural and industrial traffic in the region. The Arkansas Department of Transportation completed signage and upgrades by 2021, including the segment from U.S. Highway 49 to Highway 91. A corridor study is ongoing to evaluate extensions and improvements. Business routes of Interstate 55, also known as business loops, provide access to local communities and historic alignments, primarily in and where six such routes exist. These are all loops, signed with a green Interstate shield featuring a business plate, and no business routes are posted in , , , or . They typically follow former or local arterials through city centers. In , the New Madrid business loop covers 5.75 miles between exits 44 and 49, routing traffic east along U.S. Routes 61 and 62 through the residential areas of New Madrid before turning north to rejoin I-55. It combines with the U.S. routes to serve the town's port and historic sites along the . The Cape Girardeau–Jackson business loop spans 15.70 miles from exits 93 to 105, directing travelers east into Cape Girardeau via U.S. Route 61 (Kingshighway) and west through Jackson on a five-lane section of Route 34. The Jackson portion received AASHTO approval on April 9, 1994, to accommodate growing suburban development and tourism near the . Further north, the business loop is 5.1 miles long between exits 174 and 178, joining U.S. Routes 67 and 61 (Truman Boulevard) and branching via McNutt Street to connect the three adjacent industrial cities. Signage is limited, and it is not always reflected on official Department of Transportation maps, but it supports local commerce along the I-55 corridor south of . In , the business loop extends nearly 14 miles between exits 97 and 105, following 6th Street, Myrtle and Spruce streets, 9th Street, Peoria Road, and Veterans Parkway through the state capital. It replaced alignments of and its business route, passing key landmarks like the Illinois State Capitol and the State Fairgrounds while providing access to services. Recent rerouting adjustments were made to improve flow through the urban core. The business loop measures 8.6 miles from exits 123 to 133, utilizing Lincoln Parkway, 5th Street, and Logan Street along a historic path. It overlaps Routes 10 and 121, serving the community named for and attractions like Railsplitter , with signage emphasizing its role in local tourism. Northward, the business loop is 9.9 miles between exits 157 and 167, primarily along Veterans Parkway as a 1950s-era bypass of downtown areas. It offers motorist services, shopping, and connections to , functioning as a key commercial artery in the twin cities while avoiding the older U.S. 66 alignment through central business districts.

References

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    I-55 - Mid-America Freight Coalition
    I-55 is major north-south route in the MAFC. I-55 begins in LaPlace, LA at I-10, traverses Mississippi, Tennessee, Arkansas, and enters Missouri in the ...
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    Interstate 55
    Stretching from LaPlace, Louisiana to Chicago, Illinois, Interstate 55 travels 964 miles. The freeway connects Jackson, MS, Memphis, TN and St. Louis, MO.
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    Interstate 55 Corridor Upgrades in Jefferson County
    The I-55 Corridor Improvements project area includes the cities of Pevely, Herculaneum, Festus, and Crystal City.
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    Interstate 55 Louisiana - AARoads
    Interstate 55 travels 66 miles in southeastern Louisiana from LaPlace north between Lakes Maurepas and Pontchartrain to Hammond and Kentwood.
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    Manchac Swamp Bridge is one of the longest bridges in the world ...
    One notable feature of the Manchac Swamp Bridge is its length, measuring approximately 22 miles (35 kilometers). This makes it one of the longest bridges in the ...
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    Manchac Swamp Bridge - Atlas Obscura
    Jul 17, 2013 · 120,440 feet of concrete overpass was constructed over the Manchac swamp in 1979 to accommodate road traffic.
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    Interstate 55 Mississippi - AARoads
    May 2, 2023 · Interstate 55 travels the height of Mississippi from Pike County and McComb north to Jackson, Southhaven and the Memphis metropolitan area.
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    None
    ### Path of Interstate 55 through Mississippi
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