Opening for revenue service in 1993, the first MetroLink line was a major accomplishment for the St. Louis region.  Traversing three counties and two states, the 19-mile starter line first opened with 17 stations, 3 additional stations opening in 1994.  The line runs from Lambert International Airport in St. Louis County to East St. Louis, Illinois, via Forest Park and downtown St. Louis.

The 1993 line reutilized former rail facilities, including the rail deck of the 1874 Eads Bridge over the Mississippi River, the 4,880-foot double-tunnels under downtown St. Louis from Eads Bridge to Mill Creek Valley, and the former Wabash rail right-of-way through Forest Park and St. Louis County.  By reusing these previously underutilized assets within fortunate proximity to popular destinations, the first 19-mile MetroLink line cost only $464 million for its 1990-94 construction, the federal share approximately 80%.

Initial studies regarding the development of a rapid transit system in the St. Louis region had begun in the mid-1970s.  In 1982, the decision was made to begin planning for an initial light rail line from East St. Louis to Clayton.  An AA/DEIS was completed in 1984, leading to a decision by the East-West Gateway Board of Directors to proceed with the implementation of a light rail line from downtown St. Louis west to Forest Park and then northwest to Lambert Airport via University of Missouri-St. Louis.  Preliminary engineering on this 19-mile line began in 1985.    

The 1984 Board decision also authorized staff to explore the potential for expanding the planned line into a regional light rail system, starting with a line further into St. Clair County, Illinois.  Nine additional corridors within the St. Louis region would subsequently result, following this 1984 action.