Transit planning along the Airport/Central Corridor began as early as 1971, when it was selected as the region's primary target for further study. In 1983, funding was approved to evaluate five mode alternatives, which culminated in a 1984 draft environmental impact statement. After a series of public hearings, the East–West Gateway Coordinating Council, a council composed of the region's local governments, adopted light rail as the preferred mode alternative. The project's capital expense budget was $287.7million, which covered design and engineering, procurement, construction, and testing.
Route
The Red Line MetroLink alignment begins at Lambert St. Louis International Airport, making stops at the main and east terminal stations. It then proceeds through Kinloch before making a stop in North Hanley near Bel-Ridge. It makes 2 stops at the University of Missouri St. Louis located in Normandy. After departing UMSL-North Station, the trains divert south onto the former Wabash/Norfolk & Western Railroad's Union Depot line that once brought passenger trains from Ferguson to Union Station. It further follows into 2 stops in Pagedale on St. Charles Rock Road and Wellston on Plymouth St., before crossing the St. Louis City/County boundary line at Skinker Boulevard; and making a stop at Delmar Boulevard, serving the popular Delmar Loop and located just below the original Wabash Railroad's Delmar Station building. The Red Line meets up with the Blue Line at the Forest Park-DeBaliviere station. From this station to the Fairview Heights station in Illinois, it creates the Shared Alignment track with the Blue Line. It terminates in Shiloh next to the Scott Air Force Base and close to the Mid-America Airport in Mascoutah.
Some of these extensions will make the Red Line one of the longest light rail lines in the United States.
St. Clair County Extension
Phase 3 - Shiloh-Scott to MidAmerica Airport: the St. Clair County Extension Phase III will extend to MidAmerica Airport. Although design work for the extension has been completed, funding for construction hasn't been secured. It was originally part of the St. Clair County Extension Phase II project that extended to Shiloh-Scott, but was separated into its own project by the Federal Transit Administration due to projections of low ridership. If this extension had been built, it would have been on this route alone.
- Lambert Airport to St. Charles County: Possible plans to expand MetroLink from Lambert Airport northwestward to St. Charles County were abandoned after St. Charles County voters rejected a sales tax in 1996 to fund an extension; subsequently, all MetroBus service was ended. If the extension was funded, the route would have used the Old St. Charles Bridge as a crossing over the Missouri River to the City of St. Charles, St. Peters, and O'Fallon. In the near future, it may be considered a potential alignment to study.
