The Dubuque Railroad Bridge is interesting in that the east end of the bridge connects to a railroad tunnel. There isn't enough room between the river and the bluff for the rail line, so the railroad heads into the bluff, and makes a sweeping turn to the south, where it meets up with BNSF mainline.
This bridge has had a long ownership history. It began life hosting trains from the Illinois Central Railroad. The Illinois Central became the Illinois Central Gulf in 1972. This line was sold to the Chicago, Central, and Pacific in 1985, but returned to the Illinois Central in 1996. The IC merged with the Canadian National in 1999. Other railroads had trackage rights over this bridge, including the Chicago, Burlington, and Quincy and the Chicago Great Western. The CGW merged into the Chicago and North Western in 1968, but the C&NW abandoned its usage of this bridge in 1981.