From the Wiki:
Scotts Bluff National Monument in western Nebraska includes an important 19th century landmark on the Oregon Trail and Mormon Trail. The National Monument contains multiple bluffs (steep hills) located on the south side of the North Platte River, but it is named after one prominent bluff called Scotts Bluff which rises over 830 feet (330 m) above the plains at its highest point. The monument is composed of five rock formations named Crown Rock, Dome Rock, Eagle Rock, Saddle Rock, and Sentinel Rock.
The whole area is full of pioneer history and the rangers at Scotts Bluff National Monument are very nice. All in all Nebraska had by far the most friendly outgoing Parks Service.
Visit Scotts Bluff