Complex sentence: The National Monument contains multiple bluffs (steep hills) located on the south side of the North Platte River; it is named for one prominent bluff called Scotts Bluff, which rises over above the plains at its highest point.
Split into simpler sentences: The National Monument contains multiple bluffs (steep hills) located on the south side of the North Platte River. It is named for one prominent bluff called Scotts Bluff, which rises over above the plains at its highest point.