Whether it’s spotting a bear munching on huckleberries, a mountain goat scaling some rocky precipice, or a snake slithering through the desert sand, seeing the trail come alive is an incomparable thrill—and there’s no better place to get it than a national wildlife refuge. Since President Theodore Roosevelt declared Florida’s Pelican Island the country’s first refuge in 1903, the system has grown to include more than 150 million acres. We combed through them all to pick the 10 best treks in the lower 48.

Want to help keep the thrill alive? This summer, the National Wildlife Federation is hosting the Great American Campout, an initiative that asks animal lovers to pledge to camp in support of wildlife. Join the pledge at the NWF’s site.