Union Pacific has four major freight routes into Chicago, and two more busy lines featuring mostly commuter trains, plus several minor routes. Left-hand operation continues to be the general practice on all former Chicago & North Western trackage.
This part of the famed "Overland Route" runs from downtown Chicago to Clinton, Iowa, and is a former C&NW main line that is now UP's major route to the west. From downtown, it passes through Western Avenue interlocking (Metra Tower A-2), Proviso Yard, Elmhurst and West Chicago (Turner Junction). Further west, the line crosses BNSF's Aurora sub at Rochelle. Within the greater Chicago area, this is a mostly triple track main. From downtown to the suburb of Geneva, an average weekday sees as many as 100 trains. UP freights are plentiful, but so are UP/Metra's West Line commuter trains that terminate at Elburn, Illinois. No Amtrak trains travel this route.
Villa Grove Subdivision
This line extends from Chicago's south side to the town of Villa Grove in central Illinois, this subdivision once having been part of the Chicago & Eastern Illinois and later the Missouri Pacific. It is divided into two halves.
From Woodland Junction, where it is joined by CSX's ex-C&EI Woodland sub, north to Chicago, it is jointly-owned double track maintained and dispatched by UP. About 35 to 40 trains can be seen on an average day, passing through Momence, Chicago Heights, Thornton Junction and UP's Yard Center in Dolton.
South of Woodland, the Villa Grove Sub is an all-UP single track line that sees roughly 15 to 20 trains per day. Beyond Villa Grove at Findlay, Illinois, the route splits. One line heads to St.Louis with the other heading further southwest, eventually crossing the Mississippi River at Thebes, Illinois, and joining the ex-MP main line running south from St.Louis. No Amtrak or commuter trains use the Villa Grove Sub, but Metra hopes to someday begin commuter service with trains terminating at Crete, Illinois, a few miles south of Chicago Heights. For now, however, it remains little more than a hope.
Milwaukee Subdivision (formerly the New Line Subdivision)
This is an ex-C&NW all-freight bypass route that heads due south from Milwaukee but veers southwest at Valley Junction near the suburb of Northbrook. A few miles further south in the suburb of Glenview, a connection off CP's C&M Sub joins the UP line at Shermer. Most CP trains coming south from Wisconsin transfer to the New Line here and proceed on trackage rights through Deval to Bryn Mawr on the west side of O'Hare Airport. From there, they use CP's own tracks to reach Bensenville Yard. UP freights continue south, crossing over Bensenville on a viaduct, and terminate at Proviso.
This subdivision is part of the former Chicago & Alton, ex-Gulf, Mobile & Ohio route to Springfield and St.Louis, and runs southwestward to Bloomington, Illinois,
UP inherited this line from Southern Pacific, which had purchased it from the bankrupt Chicago,Missouri & Western, a spinoff from Illinois Central Gulf. From Joliet to Chicago, the track is owned by Canadian National, who also calls it the Joliet Sub. Freight traffic is moderate; UP prefers the Villa Grove Sub. However, with the completion of the Global IV intermodal hub, traffic has increased. Amtrak's St.Louis corridor trains, as well as the Texas Eagle, use the Joliet Sub, as do Metra's weekday Heritage Corridor trains running between Union Station and Joliet.
This subdivision runs between Kenosha, Wisconsin and downtown Chicago, and parallels the Milwaukee Sub south from Milwaukee, running closer to the Lake Michigan shore line. It is also a former C&NW line that featured intercity passenger trains to the Twin Cities and Wisconsin points before the creation of Amtrak.
Traffic now consists almost entirely of UP/Metra North Line commuter trains, most of which terminate at Waukegan with a few continuing on to Kenosha. Several UP freights from Wisconsin use the line to Lake Bluff, a few miles south of Waukegan, but transfer to the Milwaukee Sub via the Lake Subdivision. The Lake Sub diverges from the Kenosha at the Lake Bluff commuter station and runs southwest about a mile and a half, joining the Milwaukee Sub at KO Junction. South of Lake Bluff, traffic on the Kenosha Sub consists entirely of North Line commuter trains.
This line runs northwest from downtown Chicago through Mayfair, Deval and Barrington interlockings to Harvard, Illinois, near the Wisconsin border. This is another former C&NW route whose traffic consists almost entirely of commuter trains. The majority of UP/Metra Northwest Line trains terminate at Crystal Lake, with a few continuing to Harvard.
Beyond Harvard this is a secondary freight line to Janesville, Wisconsin. The relatively few UP trains from Wisconsin leave the Harvard Sub just west of Deval and access the Milwaukee Sub, on which they then head south to Proviso Yard. East of Deval, an occasional switch job can be found serving local industries, but the Northwest Line commuter trains dominate the action. There is no Amtrak service on this route. The Northwest and North lines join at Clybourn on Chicago's near north side for the last few miles into downtown Chicago.
In addition to the aforementioned Lake Sub, UP has several other minor routes. The Rockwell Subdivision connects UP's Global I intermodal yard on Chicago's near west side with the Geneva Sub. The Belvidere branch runs from UP's yard in West Chicago to Rockford, Illinois. One of the customers served is the Illinois Railway Museum. Remnants of two C&NW industrial branches on the north side of Chicago are still in operation: the Cragin Industrial Lead and the Weber Industrial Lead.
Until summer of 2019 here's what UP's infrastructure looked like: UP had two major classification yards: Proviso, a large hump yard located along the Geneva sub, and Yard Center on the Villa Grove sub. It had five major intermodal yards: Global I, west of downtown Chicago using yards once operated by C&NW and B&OCT; Global II at Proviso; Global III located west of the Chicago area near Rochelle, Illinois; and Global IV, opened in 2010 and located on the Joliet sub a few miles south of Joliet. In addition, intermodal traffic was also handled at Yard Center.
UP's commitment to Precision Scheduled Railroading will bring about major changes. The Proviso hump has been closed and the hump yards will be removed to make way for an expansion of the adjacent Global II intermodal facility. Global III has already been downsized; it no longer loads or unloads trains but remains open for block swapping and for local area freight movements. Eventually, Global I will be closed and operations moved to Global II when the rebuilding at Proviso is finished. Most of the Global III operations will be transferred to Global IV. Proviso will continue as a smaller, flat-switched facility.