In the mobile app, all 44,000 campgrounds will be available to view offline. You can verify this by selecting your Profile tab, then select PRO Tools and you'll see Campground Database and My Map Downloads.
Campground Database is a comprehensive list of all of the campgrounds listed on The Dyrt. Periodically refresh this list by selecting Refresh Data to have access to all the newest additions, deletions and updates to campgrounds.
My Map Downloads are the downloaded versions of the maps you want to view while offline.