This excellent hotspot is located in downtown Joliet, one of Chicago's largest suburbs. The station is about 40 miles southwest of Chicago and has been beautifully restored. It now hosts banquets, weddings and similar events, and though it no longer serves as a place for boarding trains, it still provides a nice place to view and photograph them. To get there, take the Dan Ryan Expressway, then I-57, to I-80. Head west on I-80 to Joliet and exit at Illinois Rte. 53. Proceed straight north on Martin Luther King Drive (formerly Chicago Street). After a mile or so you will pass under a railroad bridge. Directly in front of you will be a parking lot. Pull into the lot and park--it's free on weekends but otherwise you'll have to pay. Another lot closer to the station can also be used; it has parking meters that are in effect at all times. The station is just east of the two lots.
There's another way to get there: by train. Take one of Metra's Rock Island District trains; they terminate at a new boarding platform (opened in 2016) across the tracks from the station. As an added bonus, you'll get a nice bird's eye view of Blue Island Crossing just past the Vermont Street station (choose a seat on the right side of the train). In downtown Chicago, Joliet trains depart from La Salle Street Station, not from Union Station. The station is behind an office tower at the intersection of Van Buren and La Salle streets. A walkway on the west side of the building provides access to the station.
Four north-south tracks cross a single east-west track at the station, which is located in the junction's northwest quadrant. The two north-south tracks nearest the station are BNSF's ex-ATSF main line to the west coast. The other two are the ex-Gulf Mobile & Ohio main line to Springfield, Illinois and St. Louis. The tracks are now the property of Union Pacific (who inherited them from Southern Pacific), but just north of here ownership shifts to Canadian National (inherited from Illinois Central). The east-west track is the ex-Rock Island route. It is now owned by Metra, the Chicago area commuter train authority, from Chicago to Joliet. From Joliet to Bureau, Illinois, the line is operated by CSX, and west of Bureau it belongs to Iowa Interstate. An occasional CSX or IAIS freight can be seen on this line, but Metra commuter trains no longer cross the diamonds, terminating instead at the new platform just to the east. Weekdays, Metra trains run hourly in each direction except of course during rush hours when the frequency is greater. Weekends, they run every two hours.
By far the greatest number of freight trains are on BNSF, nearly 50 trains a day most of them intermodals. The UP/CN line sees much less freight traffic, perhaps eight or ten trains. However, a total of eight Amtrak trains to and from St. Louis stop at Joliet, including the Texas Eagle. This line also has its own Metra commuter trains (grandly called "Heritage Corridor" trains) but service is limited--only three a day in each direction during rush hours with no service on weekends. But the main reason for visiting here is the BNSF Transcon. A steady parade of trains pound the diamonds, and since you're on the south side of the tracks, photos are easy to come by.
A tower stands directly across the four track main from the station but was shut down in May, 2015. Known as "UD," it was manned by Metra operators. In 2018 it was restored and is now a museum with pistol-grip machine still in place. It is definitely worth a visit and provides an elevated view of the interlocking. A connecting track in the southeast quadrant links Metra and UP. The Heritage commuter trains use it to reach Metra's coach yard east of the station.
About a mile east of the station, the Metra line crosses the main line of the Elgin, Joliet & Eastern ("the J"), acquired by Canadian National in January, 2009. However, there are more accessible places to view it (e.g. Griffith, Matteson and Chicago Heights), and the area around the crossing reportedly is not very safe. CN/EJE has a major yard at the north end of Joliet; a good bird's eye view of it may be had from the Jackson Street overpass.
BNSF: 160.650, 160.830
UP/CN: 160.920, 161.280
IAIS/CSX: 160.230, 160.290
The station platforms are public property, so trespassing is not a problem. To access the closed off boarding platforms, use the outdoor stairway on the west side of the building. When the station was closed for train access, a waist high fence was added to the platforms but sightlines are still good. As mentioned above, a new boarding platform for the Metra Rock Island trains was built east of the BNSF and UP tracks, so Metra trains no longer cross them. The new platform is easily accessible and worth exploring. A second platform has been constructed along the UP tracks and is used by Amtrak and Metra's Heritage trains. It is highly recommended since it provides a nice view of the old station as a backdrop. In 2018 a new Amtrak terminal building was completed and provides access to both the platform and UD tower.
For more on Joliet Station, along with plenty of photos, see Ron Goodenow's Attic.