Then, by all means do plan to visit on a Saturday or Sunday, it is only about 1.5 hours from downtown Chicago or about 70 minutes from ORD. It seems silly to travel that distance and not visit especially if you are a rail fan.
If you have ever watched the movie "A league of their own" you may recognize the train and all the train scenes that were filmed there. In fact many movies are filmed here, just look for any vintage diesel or steam power with overhead catenary above the track, it kind of gives it away.
You may also like the Rochelle train watching platform as it is open every day, and is usually filled with many train watchers from all over the world, who would like to converse with anyone within earshot. It is about 30 minutes from Union and about 2 hrs due west from Chicahgo on the UP mainline and BNSF line to the Twin Cities and Pacific Northwest. At an average about 40-60 trains a day (mainly freights, coal drags and containers, and other manifests) pass the junction daily. Plus it has a web cam. Just google Rochelle train cam and you should find it.