Most Yellowstone National Park campsite reservations open up months in advance. However, it's notoriously difficult to secure a Yellowstone reservation even if you plan ahead, as campsites are often booked up within minutes. To increase your chances of snagging a campsite, set up a free Hipcamp alert for any Yellowstone campground. We'll monitor campground availability, and you'll get instantly notified of any openings that come up for your dates so you can jump on it to reserve the newly open site. Set up an alert.