The best source I have found for CampGrounds, Walmart locations, COE campgrounds, Escapees, etc camping is here
All of their information is in the form of map overlay files for the following programs:
1. Delorme Draw Files â€“ can only be used by Delorme Street Atlas
2. MS Streets Files â€“ can only be used by MS Streets and Trips (Note 1)
3. CoPilot Files â€“ Text files for import to CoPilot (Note 1)
4. Text Files â€“ for use with GPSBabel to convert to other formats
5. Google Earth â€“ for use with Google Earth
This is probably more information than you will ever want on campground locations.
I travel with a laptop hooked to a GPS antenna and I use the DeLorme TOPO 7 software. This combination has so many options and displays a full screen map of your route.I can load all the DeLorme overlays and switch them on and off as needed. - A 17" map is a lot easier to read than a 4" one- I had a Garman and found DeLorme to be a much better solution for travel in the RV.