It really depends on where you want to go, I would make the recommendations of State Line Tower, Dyer IN.
But my favorite location of all time is: Rondout (If you want to make the drive!)
Black Sheep 25
"Do not lead me into temptation, I can find it myself!"
I'll echo what DAKguy says, and add that if you prefer not to drive all of the way out to Rochelle (about 1.5-2 hrs from downtown Chicago and one of my favourite spots), you can always take a UP-W Metra train to the Elmhurst station and hang out on the platform there, where you can see UP action heading into/out of Proviso yard. Tickets are $3.80 single on weekdays or on weekends there is a $5 pass for unlimited travel on all Metra lines.
I see you are interested in freight, but if you are staying downtown and will be around during the weekday rush hour period, try to check out the leads to Union Station. It's easy to watch action on the north lead from the Lake St. overpass just west of the river (and you can also see the leads to Ogilvie Station from this vantage point). For the south leads, you can go to the Roosevelt St. overpass, where you can also see the Amtrak facilities.
Joliet is a great choice, and you can take METRA (the local operator of commuter trains) to get there. I believe they have recently finished a railfan pavilion which would be a great location for watching or photography (I believe you will be on the east side of the tracks, so try mornings).
The other classic place with a pavillion is Rochelle, but you need an auto to get there. In terms of geography you will be on the south side of the UP tracks, and the northeast side of the BNSF.
If you are downtown and appreciate buildings, be sure to take in Union Station. The portion that is the access to the platforms is the typical commuter rabbit warren, but find a station diagram and go to the portion they call the Great Hall.
There are many other good locations in the Chicago area, but I hesitate to recommend them to a foreigner who may not recognize signs of our more dangerous neighborhoods.
And, by the way, welcome to the US!
I recommend Dolton Tower and Blue Island. Word to the wise don't do any trepassing on railroad property, they don't play around in Chicago anymore.
Myself and 6 other rail fans are coming over to USA in 2 weeks time, and would like to know best places to see/photograph Freight in the Chicago area
Have heard Joliette is worth a look, anyone recommend some other places?
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