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| Interstate 255 (Missouri) | |
|---|---|
| State | MO |
| Route | 255 |
| Length mi | 30.85 |
| Established | 1983 |
| Direction a | West |
| Terminus a | Missouri River near St. Louis |
| Direction b | East |
| Terminus b | I‑270 in Mehlville |
| Counties | St. Charles County, St. Louis County |
Interstate 255 (Missouri) is an auxiliary Interstate Highway forming a semicircular bypass around the southern and eastern suburbs of St. Louis on the Illinois side of the Mississippi River and the Missouri side across the river loop. The route connects major corridors including Interstate 55, I‑64, Interstate 44, and I‑270, serving industrial, commercial, and residential districts in East St. Louis, Mehlville, and Arnold. The highway integrates with regional freight and commuter patterns influenced by facilities such as Lambert–St. Louis International Airport, the Port of St. Louis, and the Chain of Rocks Bridge corridor.
Interstate 255 begins at a junction with I‑270 near the southern limits of Mehlville and proceeds eastward through St. Louis County suburbs, intersecting state routes and municipal arterials that provide access to Jefferson County bedroom communities and employment centers tied to Anheuser-Busch facilities and the National Geospatial-Intelligence Agency St. Louis campus. The freeway crosses the Mississippi River via the McKinley Bridge-adjacent crossings and links to I‑55 near industrial zones that serve the Union Pacific Railroad and BNSF Railway freight networks. Eastbound, the corridor skirts the Missouri Botanical Garden influence zone and connects with U.S. Route 50 and U.S. Route 61 feeders that distribute traffic to shopping centers anchored by national retailers and regional hospitals affiliated with Barnes-Jewish Hospital partnerships. The design accommodates heavy truck flows to the Port of Metropolitan St. Louis facilities, with grade separations near the Missouri Pacific Railroad rights-of-way and interchanges serving the St. Louis Lambert International Airport approach corridors.
Planning for the southern bypass that became I‑255 originated during the post‑World War II interstate expansion era influenced by the Federal-Aid Highway Act of 1956 and metropolitan planning by the East‑West Gateway Council of Governments. Initial routing proposals paralleled historic turnpikes and riverfront freight routes used during the Missouri Compromise era transportation evolution and were debated in hearings involving representatives from St. Louis County, St. Charles County, and the Missouri Department of Transportation. Construction phases during the 1970s and early 1980s reflected coordination with U.S. Army Corps of Engineers river management projects and mitigation commitments with the Environmental Protection Agency regarding wetlands near the Mississippi River Basin. The corridor opened incrementally, with major interchanges completed alongside expansions of I‑55 and the rebuild of the Chain of Rocks Bridge approaches, ultimately achieving full designation in 1983 after federal approval by the American Association of State Highway and Transportation Officials.
The route includes directional interchanges and collector–distributor systems serving urbanized nodes: the west end near I‑270 provides connections to St. Louis County, Mehlville, and Arnold; intermediate exits serve U.S. Route 50, U.S. Route 61, and state routes that access Cahokia Heights and East St. Louis industrial areas; eastern termini tie into I‑55 and feeder ramps that distribute traffic toward Springfield, Illinois and the Gulf Coast. Major interchange nodes link with arterial corridors used by commuters to Downtown St. Louis, tourists visiting the Gateway Arch National Park, and freight serving the Port of St. Louis. The highway features service areas and emergency turnout points coordinated with Missouri State Highway Patrol and Illinois State Police jurisdictional responsibilities.
Planned improvements to the corridor focus on capacity, safety, and multimodal integration coordinated by Missouri Department of Transportation and the Bi‑State Development Agency. Projects under consideration include interchange reconfigurations near Route 3 to improve access to Scott Air Force Base logistics nodes, pavement rehabilitation linked to federal funding under subsequent Surface Transportation Reauthorization measures, and freight efficiency upgrades to support links with MidAmerica St. Louis Airport and river terminals. Environmental reviews reference consultations with U.S. Fish and Wildlife Service regarding riparian habitats and with National Park Service stakeholders near the Gateway Arch National Park. Local governments including St. Louis County and St. Charles County have proposed transit‑oriented development around major nodes to connect with MetroLink expansions and Amtrak corridors.
I‑255 functions as an auxiliary of I‑55 and interfaces with primary interstates: Interstate 44, I‑64, and I‑270. It supports truck movements linked to Class I railroads including Union Pacific Railroad and BNSF Railway and integrates with regional transit providers such as Metro Transit and intercity services like Greyhound Lines and Megabus. Connector routes and parkway systems in adjacent counties—managed by entities like the East‑West Gateway Council of Governments and Bi‑State Development Agency—enable coordinated planning for freight, commuter rail, and highway resiliency in events coordinated with Federal Emergency Management Agency preparedness programs.