9. Bering Land Bridge National Preserve, Alaska

Number of visitors in 2018: 2,642

This roadless wilderness sits on the western edge of Alaska in an area known as the Seward Peninsula. Though few people travel here today, archaeologists believe that ancient populations migrated from Russia into the Americas across this stretch of land during the Ice Age 10,000-12,000 years ago when ocean levels dropped and exposed a 1,000-mile path between the continents. Once the stomping grounds of mastodons and mammoths, the preserve is now home to reindeer, muskox, wolverines and other hardy animals, and is also a nesting site for birds traveling the Asiatic-North American Flyway. A few of the preserve’s most unusual features include towering rock formations known as tors, hot springs with year-round geothermic activity, and the four largest maar lakes in the world. Maars are craters created when magma from a volcano makes contact with groundwater (or, in this case, permafrost), causing a large explosion of steam. A typical maar might measure 1,000 feet across; the largest maar at Bering Land Bridge is more than 5 miles wide.