Mount Rushmore in the Black Hills of South Dakota is a neat place to visit, if you don't mind crowds.  I took these photos of Mount Rushmore in 2004.  The monument is impressive but there is a giant building and parking complex built around it, so it feels like going to an amusement park.

There are many other interesting sights to see in the Black Hills region, including Badlands National Park, Wind Cave National Park, and Jewel Cave National Monument.  Don't forget the Minuteman Missile National Historic Site.  Devil's Tower National Monument is also in the region.