It's not free but if you buy the road atlas in Walmart there is usually a section in the back about the different Walmart locations and if I remember correctly there was something about overnight stays or camper friendly locations listed as well. With that being said...we've found it more expensive to stay at Walmart than at a campground. We would pull in and go in the store to stretch our legs" and grab a few things". A few things would turn in to a few things we didn't think of and next thing you know it cost more than a campground...and no hookups. We have done and still do the Walmart thing on occasion. It's generally a good place to pull in and rest but it's not a money saver if that's what your after.
