Grand Staircase-Escalante National Monument, Utah

Named for the stair-stepped cliffs that descend from Bryce Canyon toward the Grand Canyon, this nearly 1.9-million-acre monument holds slot canyons, waterfalls and some of the richest late Cretaceous fossil beds in North America. Established in 1996, it remains largely undeveloped — most of its canyons, plateaus and badlands are reached by unpaved road or trail, making it one of the last great wild landscapes in the Lower 48.