BNSF is the easiest railroad to describe. It enters Chicagoland via just two routes, both of which see over 40 freights per day. Both are controlled by dispatchers in Ft. Worth, Texas.
This is the former Burlington Northern (Chicago, Burlington & Quincy) triple track main line (the "racetrack") between downtown Chicago and Aurora. The Chicago sub extends west from the Canal Street Wye, passing through Union Avenue, LaVergne, Congress Park and LaGrange on its way to Aurora. In addition to BNSF freights, UP trains on trackage rights can also be seen. Metra commuter trains use the line extensively, terminating at Aurora. Amtrak's California Zephyr, Southwest Chief and corridor trains to Quincy, Illinois, also use the Chicago sub. An average weekday sees about 100 trains. On the west side of Aurora, the route splits. The Mendota Subdivision extends from Aurora to Galesburg, Illinois. Beyond Galesburg, this line reaches west to Omaha and Denver. The Aurora Subdivision runs from Aurora through Rochelle to Savanna, Illinois, and from there the line runs along the Mississippi River to the Twin Cities and points west.
This line extends from approximately Corwith Yard on Chicago's south side to Fort Madison, Iowa. At one time it terminated at Chillicothe, Illinois, but was extended to Fort Madison in the 1980s. The Chillicothe runs from Corwith in a southwesterly direction through McCook Junction and Joliet Station. This is the famous ex-Santa Fe "transcon" main line to Kansas City and the west coast. It features all kinds of freight traffic but time-sensitive intermodal trains are dominant, with many serving the large UPS terminal at Willow Springs or the Logistics Park terminal west of Joliet. No commuter or Amtrak trains operate on this sub.
BNSF's major yards in the Chicago area are Cicero Yard on the Chicago sub and Corwith Yard on the Chillicothe. Both have evolved into major intermodal terminals. In addition to Willow Springs, the Chillicothe is also home to Logistics Park, a large intermodal and warehousing facility southwest of Joliet. Constructed in 2005, it occupies the former Joliet Arsenal military site. Most carload traffic is handled at Eola Yard or else delivered to Clearing Yard (Belt Railway of Chicago). Cars bound for those yards are sorted and pre-blocked at Galesburg, Illinois. The majority of auto rack traffic is delivered to Indiana Harbor Belt's Gibson Yard.