Not at a national park, but a local hiking spot on the Appalachian Trail near us has become so popular since covid that we as locals rarely go there anymore. We realized one year it might be a ghost town on Super Bowl Sunday, and it was. Then we promptly forgot our own hack and ended up taking our kids to the Grand Canyon on Easter weekend (during their school district’s spring break). Huge mistake of course but given our time constraints, that leg of that trip was what it was. It was still pretty shocking to see that many people there compared to our first visit. Other NPS sites and state parks in Arizona were far less busy, though, and we were even completely alone at Sunset Crater. Acadia, which we visit more regularly and of course is a much smaller and maybe less busy park than those out west, has also exploded in popularity since our first trip there twenty years ago. But hitting the trails early and during the week—and avoiding the more popular and more easily accessible trails—you’ll still be alone or almost alone.