Keith:
Not sure if there are any dumps in the Joliet area as I live in NH, but I can give you a little advice and make some suggestions based on what I do.
1. Research, research, research
2. There's no magic formula
3. You have to get outside and look
4. Go to the local diner and/or town gathering place and ask old timers
5. Old topo maps from the 1930's to 1960's are a great way to see where people lived back in the day. Look for little squares along roads, rivers and especially lakes. Check out this link
https://store.usgs.gov/ and go to "Map Locator" and type in Joliet, IL. Then scroll down to an older map and click save as a PDF to your computer, tablet and/or mobile phone. Then you can view the map.
6. Google Earth is a great "current day" frame of reference for what's there now. It's a great tool to see if that house/cabin on the 1940's map is still there.
7. Look for places where people went back in the day (hunting/fishing cabins, lakes, etc.)
8. Old town dumps were typically +/- 1/4 mile outside of town. Many of these have been cleaned up and lined and capped, but you never know.
9. Dirt two track roads off state routes into the woods are always worth checking out
10. Turn offs with steep banks are great to check as the trash would be thrown over and it would be out of sight.
Good luck hunting.