The Recreation.gov reservation window, and what "sold out" means
3,489 of the 5,569 campgrounds on this site have a booking page on Recreation.gov. That is 63 percent. Each of those campground pages links to its Recreation.gov page. The booking rules described below are Recreation.gov's, taken from the site's help center. This site does not book anything and does not hold availability data.
How the window works
Recreation.gov's help center says most campgrounds open sites for reservation on a rolling basis a set number of months before the arrival date, with new dates released each morning at 10 a.m. Eastern. The help center describes six months as the common window for individual campsites and says some facilities use a different one. Group sites and some cabins open further out. A few campgrounds release sites only days ahead.
The window belongs to the campground. The managing agency chooses it. The campground page on this site does not state the window, because Recreation.gov does not publish it in the data feed this site uses. Open the campground's Recreation.gov page and read its booking information. When a campground's own text mentions its window, that text appears on this site under "Charges and cancellations" or "Know before you go", quoted from the record.
What the release morning looks like
On the release morning the new date appears on the calendar at 10 a.m. Eastern. At campgrounds with high demand the popular sites go within minutes. The help center explains that Recreation.gov holds a selected site for a short time while you check out, and that the hold expires if the order is not completed.
A workable plan is to be logged in before 10 a.m. Eastern with the campground page open, the date range set, and a second-choice site picked. Recreation.gov requires an account to book, and creating one takes several minutes.
What "sold out" means
When the calendar shows a date as unavailable, the help center gives several possible reasons. The site may be reserved by someone else. The date may not have been released yet, because it is beyond the campground's window. The site may be closed for that date, for maintenance or for the season. The campground may hold some sites back for walk-up campers, and those never show as available online.
An unavailable date is therefore not always a booked date. Check the campground's season on this site and on Recreation.gov before concluding the campground is full. A campground that is closed for the winter shows every date as unavailable.
Cancellations and the days before arrival
Reservations get cancelled. The help center describes a cancellation fee and a late cancellation cutoff, and a cancelled site returns to the calendar once the cancellation is processed. Checking a booked campground in the week before your dates is how many campers get a site. The fees and cutoffs are in the help center and on each reservation. This site does not track them.
Walk-up sites at reservable campgrounds
Many reservable campgrounds keep a share of sites for campers who arrive without a booking. Recreation.gov does not show those sites on the calendar. The campground's text on this site sometimes mentions them.
When the calendar is full, the first-come list has 2,642 campgrounds with first-come sites. 2,080 of them never take a reservation, and the reservable list shows every reservable campground by state, so you can see which neighbors also have a booking page. The guide to how first-come campgrounds work covers the walk-up side of the same trip.