I can say that I've never heard of a free mobile home. Until now. There really is a free mobile home and it's only about 3 hours from Casper.

This is what I found on Wyoming Craigslist.

Wyoming Craigslist

Technically, this is in northern Colorado in Wellington. That's an easy 3 hour jog from Casper. Here's what the owner said on Craigslist:

Free!!!!! 1970 Schultz mobile home. Decent shape. Needs to be moved by 3/12/2019. Colorado title on hand no axles or wheels

If you are into fixer upper projects and have the ability to move this, could be quite a bargain. Check out the full Craiglist description to see if this beauty would look good on your lot.