A trip to Devils Tower National Monument involves an hour detour from I90, a 1.6 mile loop hike around the rock formation, stopping at the Visitor Center, and enjoying the prairie dog towns.
Visiting Mount Rushmore National Memorial
After a day at Custer State Park, visit Mount Rushmore just before dusk. Take pictures in the daylight, watch the movie at the visitor center, and walk along the Presidential Trail. Attend the lighting ceremony (in the summer months), and enjoy the monument as the sky darkens. There is a café at the memorial, which is open until 6:30pm.