The directory profiles every campground that participates in the program. It includes state and local maps, directions to each campground, rates, phone numbers, campground highlights and facilities information. Most parks don't require reservations. The ones that require or recommend reservations are noted in the directory. This year most parks have had plenty of space available, but I call ahead just to be sure.
Most parks have no limits on the length of stay.
The ones that limit the stay are listed in the directory. Also, there is no limit to the number of times you use the program. Stay at one park or dozens. Some of my travel buddies are pretty skeptical. Here's what they asked me.