Map of the Chicago & Alton, turn of the century
The Alton was one of the more important railroads in the early history of Illinois, being one of the so-called air lines -- meaning that it followed a very direct route, in this case to Saint Louis and Kansas City and to the cities in between. When the Santa Fé railroad opened in 1888, however, that became the more direct route. The Bridgeport segment of the Alton was in actual fact the Joliet & Chicago railroad, but it had been perpetually leased by the Chicago & Alton from the early 1860s onward. The line later became part of the Gulf, Mobile & Ohio railroad, which itself was merged with the Illinois Central railroad to form the Illinois Central Gulf railroad. Although the depot is long vanished, this line still runs through Bridgeport today.

Source: The Chicago and Alton Railroad/The Chicago and Alton Railway... (New York: N. W. Halsey, 1905).