St. Louis Freight Tunnel
The St. Louis Freight Tunnel is a historic railroad tunnel beneath Washington Avenue and Eighth Street in downtown St. Louis. Completed in 1874, it carried freight and passenger trains between the Eads Bridge and the rail yards in the Mill Creek Valley, bypassing busy downtown streets. Today it is used by MetroLink, the light rail system in Greater St. Louis. History 

City leaders had wanted a wagon bridge to the heart of the city to highlight downtown St. Louis. However, economics required that it be a railroad bridge, but there was no space for railroads on downtown streets. Therefore, a tunnel was authorized to connect the Eads Bridge to the Missouri Pacific Railroad to the south (and later to Union Station). The designer of the Eads Bridge, James B. Eads, worked out the specifications for the tunnel. It would be a cut-and-cover tunnel  long and  below street level. A smokestack with a fan that pulled exhaust from the tunnel was built near St. Charles Street (it has since been demolished). Several problems arose during construction of the bridge and tunnel including design changes, inflated land and labor costs, and renegotiated contracts that escalated construction costs 46% over initial estimates. The tunnel structure was completed by June 24, 1874, and the bridge would open less than a month later on July 4. When it first opened, the tunnel had few users and had already been spun off as the St. Louis Tunnel Railroad Company led by William Taussig. At the time, many railroads did not have licenses to operate in Missouri and by 1875, the company defaulted on its debts and a federal court appointed J.P. Morgan and Solon Humphreys as receivers. Also in 1875, Taussig would supervise the opening of the first Union Depot on Poplar Street, between 11th and 12th streets near the mouth of the tunnel. In 1878, the newly formed St. Louis Bridge Company purchased the bridge and tunnel out of bankruptcy for $2 million, about a third of its original cost, then transferred it in 1880 to interests controlled by Jay Gould. In 1889, Gould would be instrumental in the creation of the Terminal Railroad Association of St. Louis (TRRA). He died in 1892, but his involvement in the TRRA led to the construction of Union Station in 1894. In 1974, due to the increasing dimensions of railroad cars, the tunnel saw its last train; an Amtrak passenger train. Passenger and freight rail traffic then switched to the Merchants and MacArthur bridges. MetroLink 

In 1971, regional transit planners identified the Airport/Central Corridor alignment as the region's primary target for further study. In the 1987 draft environmental impact statement, light rail was selected as the region's preferred mode alternative. In 1989, after it was determined the downtown portion would use the Eads Bridge and existing tunnel for light rail, the city of St. Louis swapped the MacArthur Bridge for the Eads Bridge with the Terminal Railroad Association. In 1991, rehabilitation began on the subway tunnel for MetroLink usage with it reopening in 1993. In 1992, just east of the present day Convention Center station, a portion of the tunnel beneath Washington Avenue and Broadway collapsed, injuring no one. Architecture 

The tunnel is notable for its brick and stone construction. It's foundations are made up primarily of Aux Vases sandstone while the upper portion of the tunnel is constructed of brick barrel vaults. In the subway stations that were cut into the tunnel, the ends of the platforms are met with brick archways that complement the arch motif used throughout the MetroLink system. Station listing

References 

MetroLink (St. Louis) infrastructure
Tunnels completed in 1874
Railway tunnels in Missouri