The rail bridge in the background was built when the Canal was built by the Rock Island Lines, subsidiaries, the Rock Island & Peoria Railroad, and the Rock Island and Mercer County Railroad (RI&MC). The bridges it connected to were built across the Rock River by the Rock Island & Peoria Railway in 1856. The Rock Island Southern (RIS) had traffic rights over the rail bridge that they obtained from Southern Junction between Reynolds and Preemption to Rock Island. When the Rock Island lines abandoned the RI & MC in the 1920s, and then the line from Milan past the old Eagle warehouse to Orion through Coal Valley in 1941, the RIS continued to use the bridge and line to Rock Island until 1952 when it ceased operations. The Rock Island Lines then took over the branch line and continued to operate it to Milan to serve Eagle and the businesses along Andalusia Road. Today, the line that was not abandoned by the Rock Island is part of the Iowa Interstate.
There were two swing bridges across the Canal at Milan. The railroad bridge was replaced in the late 60's or early 70's by the culvert and fill across the canal and is still used by the Iowa Interstate to reach the industries in Milan on the old Milan sub of the Rock Island Lines. The Rock River bridges were originally built by the Rock Island & Peoria Railway which as owned by the Cable family that also managed the Chicago Rock Island, and Pacific, the Rock Island Lines. When the Hennepin Canal was built, the swing bridge was built so boats could pass. The remains of the turntable in the canal are from the US 67 Highway Bridge that was replaced in the late 40's after the span closest to Rock Island that was right next to the Sears Power Dam collapsed. The tracks that exist were the street car tracks. The Rock Island and Peoria went through Milan and behind the Quad City Airport and then along US 150 through Coal Valley to Orion. The line was abandoned between Milan and Orion in 1941, and the Rock Island secured trackage rights over the Burlington from Colona to Orion to reach the remaining trackage through Cambridge to Peoria. Branching off at the Milan depot was the Rock Island and Mercer County Railroad, also owned by the Cables, to reach their coal mines in Preemption, Sherrard and the town of Cable. The Rock Island Southern leased trackage rights on the line from Southern Junction near Matherville through Milan to reach Rock Island. The lines south of Milan were abandoned in 1952 when the RIS shut down.
1910 topo shows a combined road and interurban line. The RR is most likely the Rock Island Southern Interurban. The Rock Island line crossing shows in its present location.
Entry for that bridge: https://bridgehunter.com/il/rock-island/ri-hennepin-canal/