Want to visit the country’s most popular national parks but can’t seem to score a campsite? That’s probably because you haven’t booked months, if not up to a year, in advance. Even if a last-minute spot opens up, chances are the place will be packed: your tent butting up against a stranger’s picnic table, the sound of humming generators buzzing nearby. That’s not a wilderness experience we’d recommend. We’ve done some digging to uncover the spots to camp near our favorite national parks—all of which are within an hour of an entrance gate—that guarantee availability and respite.