In 1889, the Terminal Railroad Association of St. Louis was formed as a switching company to connect railroads on both sides of the Mississippi River.

The original line was charted in 1866; and included a single bridge across the Mississippi River. The St. Louis and Illinois Bridge Company is rewarded with a charter to build the bridge; albeit with numerous restrictions.

The first train of this bridge, known as the Eads Bridge, would cross the bridge in 1874. The line would connect downtown St. Louis to Illinoistown (later East St. Louis).

Another line was built in 1890 by the St. Louis Merchants Exchange, and included another massive bridge across the Mississippi River designed to combat the prices of the Eads Bridge.
Eventually, these two bridges would be merged into the Terminal Railroad Association. The TRRA was masterminded by Jay Gould; and included:
The Missouri Pacific Railroad; the St. Louis, Iron Mountain and Southern Railway; the Wabash Railroad; The Ohio and Mississippi Railroad; the Louisville and Nashville Railroad; as well as the Cleveland, Cincinnati, Chicago and St. Louis Railway (Big Four).

The Rock Island eventually joined the TRRA in 1902. The TRRA opened a number of switching yards in the much more industrialized East St. Louis, Illinois.

Presently, the TRRA operates a number of lines throughout the same area. The two bridges across the Mississippi River include the Merchants Bridge, and the MacArthur Bridge.
The MacArthur Bridge was acquired in a trade in 1989 for the Eads Bridge with the city of St. Louis.

Today, Union Pacific is the largest stakeholder in the company. UP owns 3/7 of the company. Norfolk Southern, CSX, BNSF and Canadian National all own 1/7 each.