The first ever national monument in the U.S., Devils Tower National Monument is famous for its massive column of igneous rock visible for miles (featured in the movie Close Encounters of the Third Kind). Over half a million people visit the park annually, mostly during the summer months even though the park is open all year. Hiking is the most common activity here, though a brave few do attempt climbing the tower. Camping is available in one developed campground.
The parks relatively small size limits the length of the trail network, and the scenery on most trails focuses on Devils Tower. The Tower Trail is the easiest route in the park, a paved pathway that circles the tower after a short climb up to its base with educational signage interspersed throughout. Most visitors to the park choose this trail, so it will likely be crowded. The Red Beds Trail is the best alternative to the Tower Trail and allows you to escape the crowds on a slightly longer route with more uphill; this trail's distance from the tower provides also better views than the Tower Trail (in my opinion). The Joyner Ridge Trail is a short loop with views of the the tower from afar and is great for a hot summer day since the trail dips down into a wooded ravine that is slightly cooler than the surrounding area. None of the trails connect with routes outside of the park, so head to the Black Hills National Forest for more hikes.