I've been testing out a campground app that I've come to like, called "the Ultimate US Public Campground Project," which is based on the website project at http://www.ultimatecampgrounds.com/
The website for the app is http://modesittsoftware.com/UltimateCG/ ... Intro.html
It's for iOS and costs $5.
The list of campsites is super extensive; in going through OR, NV, UT and CO I never missed any. The info is pretty up-to-date (with obviously the exception of everything fed closing down, which occurred just as I was ending the trip). As he explains in the FAQ closure dates and costs can vary faster than they can keep up, but since the app provides contact info you can suss that out yourself.
The website has a very complete list of campgrounds, which is incorporated into the app. You can get those near you, or search. I really like that it has elevation and data like elevation; my atlases did not include that info and elevation, for example, was critical. You can search areas not near you, and use it to get directions. And it incorporates weather info at the site you're interested in.
They've incorporated an amazing area of camping sources, including utility, military, wildlife management areas, etc. Everything BUT private sites. And they include boondocking areas; e.g. it led to me to BLM open camping off I70 in UT. I knew it was probably BLM land, but it was nice to have this confirm so I didn't drive there needlessly.
The app claims to have offline capability, but although it had a blank map listing campsites nearby based on GPS the details about the camp, other than name, weren't available.
BTW, I've been discovering fewer cell holes lately. I got better ATT coverage on the (very) lonely Winnemucca to Sea highway (140) than I get at home in Oakland. Sheesh.
Anyway, hope the app gets better. Like to see links to other campsite websites, and better offline info (it looks like you can download the whole POI set at the project website; I'll look at that). The author often participates over on the Expedition Portal site, so he's obviously a fellow traveler.