This app was mentioned in 5 comments, with an average of 3.20 upvotes
If OP has an android phone, this app helped me find a nice place to stay along my cross country trip when I didn't know where I would exactly be ending up for a night in South Dakota: https://play.google.com/store/apps/details?id=com.ultimatecampgrounds.ultimatecampgrounds
Ended up in a park that had about 20 spots for RVs, with vault toilets and a water source (I think electrical outlets too in the center, but I didn't check). I was the only one there, and I got to wake up right at sunrise because I hadn't checked to see it was next to a small airfield.
I use Ultimate Public Campgrounds. It covers all public lands in the United States and Canada and a bunch of publicly-owned campgrounds, as well. If it's owned or operated by National Park Service, Army Corps of Engineers, Forest Service, Bureau of Land Management, Fish & Wildlife Service, Bureau of Reclamation, Department of Defense and Tennessee Valley Authority, it's included in the app.
It's $4. Takes some time to download the maps, but it doesn't collect your data and it doesn't mess around with subscriptions.
https://play.google.com/store/apps/details?id=com.ultimatecampgrounds.ultimatecampgrounds
I just recently finished with a 3500-mile road trip, and sought out dispersed camping along the way. I used an app on my Android to pinpoint locations... Maybe it might come in handy for you too: Ultimate US Public Campgrounds
I have Ultimate Public Campgrounds installed. It's pretty good, and allows users to rate campgrounds. Not for backcountry campsites. I wouldn't want an app that draws people to favorite spots in the backcountry. As Hunter Thompson liked to say: "Why would I shit in my own nest?"
Some apps I would recommend for your phone.
https://play.google.com/store/apps/details?id=com.ultimatecampgrounds.ultimatecampgrounds
https://play.google.com/store/apps/details?id=com.twostepsbeyond.coverage
This one requires a paid membership but worth it. https://play.google.com/store/apps/details?id=com.overnightrvparking.app
https://play.google.com/store/apps/details?id=gbis.gbandroid
https://play.google.com/store/apps/details?id=com.alltrails.alltrails
https://play.google.com/store/apps/details?id=com.roadtrippers