Here's another option.
https://freecampsites.net/
Depending on the size of your RV, the campsites offered on this app can work quite well.
Just enter the city or area you'd like info on and the app comes up with several free as well as paid options and includes GPS coordinates. The campsites are user rated and described in some detail so you can determine if they suit your needs. We use Google Earth in conjunction with the app to overview the sites as a pre-trip planning tool to determine possible stopping/camping spots.