West Chicago is a city in DuPage County, Illinois, United States. The population was 25,614 at the 2020 census. It was formerly named Junction and later Turner, after its founder, John B. Turner, president of the Galena and Chicago Union Railroad (G&CU) in 1855. The city was initially established around the first junction of railroad lines in Illinois, and today is still served by the Union Pacific West Metra service via West Chicago station.

The Union Pacific West Line (UP-W) is a Metra commuter rail line operated by Union Pacific Railroad in Chicago, Illinois and its western suburbs. Metra does not refer to its lines by particular colors, but the timetable accents for the Union Pacific West line are "Kate Shelley Rose" pink, honoring an Iowa woman who saved a Chicago & North Western Railway train from disaster in 1881. Green and yellow were already selected for the Union Pacific North Line and Union Pacific Northwest Line, respectively, so pink was chosen for this line. Therefore, the UP-W is the only Metra line that uses a color to honor a person instead of a fallen flag railroad. Until the late 1940s the line had a branch to Freeport, Illinois. It diverged from the main line at West Chicago and had stations at Elgin, Marengo, Belvidere, Rockford, Freeport, and other communities. The line was once known as the Chicago & Northwestern/West Line until UP took over the C&NW in 1995. All Metra trains on this line terminated at Geneva until 2006, when the line was extended to its present terminus in Elburn. The line runs as part of the Union Pacific Railroad's Geneva Subdivision.