It's a well-known secret that WalMart is one of the best free campsites in the US.
It helps that there are thousands of store located right off the major interstates.
At night you will often see scores of campers and RVs sitting in the far corners of the parking lot.
For a full guide check out: https://every-last-rock.com/how-to-car-camp/
Let me know what you think in the comments below!
