The first declared National Monument in the United States.

A waterfall 600 ft. inside a mountain, once the bane of gold miners, is now a spectacle of nature.

Known as "The Hill of the Little Devils."

A six-ton, 12-foot-tall concrete prairie dog is touted as the largest in the world.

A fitting attraction for the corn capital of the world.

The highest point in South Dakota contains the ashes of Valentine McGillycuudy, the "Holy White Man."

The ravine where Jesse James supposedly performed an impossible jump to evade capture.

This prehistoric sinkhole lured exclusively male mammoths to their death, much to the delight of science.

One of America's first dinosaur parks gives a window into Depression-era paleontology.

This replica stave church looks like a piece of Norway was simply plopped down in South Dakota.

A place where the laws of nature seem to have gone completely berserk... but of course haven't.

The world's largest mountain carving could fit all of Mount Rushmore inside it many times over.

The granddaddy of all tourist traps, built on ice water, jackalopes, and a giant dinosaur.

Small plaque marks the spot, but the true center is located about half a mile away on a private pig farm.

It's big, it's a ball, and it's made of twine—the world's largest of its kind.

To find the "unicorns of the deep" you've got to go downstairs.

These pretty kitties killed and ate as many as 135 railway workers.

The U.S. Fish Commission’s effort to mass produce carp.

The 5.5-mile ring of steel posts around the Capitol Building is one of the largest (and most uniform) of its kind in the world.

An overlooked memorial honoring the local Washington residents who died in World War I.

When it comes to handsignals (and colonialism) rock always beats scissors.

Those with a sharp eye can find the hidden image of a German Shepherd on the memorial's Mural Wall.

A museum cafe showcases Native American dishes and indigenous ingredients from across the Western Hemisphere.

The national park was once a plantation estate.