The last physical evidence of the Lewis and Clark trail is one of their autographs etched into this giant rock.

The first declared National Monument in the United States.

This erect, phallic geological spire wasn't always named so domestically.

When an ancient supervolcano erupted, some of Nebraska's prehistoric animals were forever preserved in ash.

One of the world's most definitive collections of musical instruments, spanning all cultures and historical periods.

At the turn of the 20th century, the Minnehaha County courthouse played host to sensational public divorce trials.

More than 7,000 gallons of water pour over these cascading red quartzite waterfalls every second.

These cliff and rock formations are made out of Sioux Quartzite.

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

These formal gardens were designed to be admired from the vantage point of the castle.

It's said this was once the home of King James V's pet lion.

These steps offer a breathtaking view of one of Europe's most besieged fortresses.

Overlooked by many, the two famous Scottish warriors guard the main gate of Edinburgh Castle.

A six-ton wedding present for the King of the Scots.

A fitting attraction for the corn capital of the world.

A striking sculpture built to honor the women of the Lakota and Dakota Nations.

Site of the 1879 Cheyenne Outbreak and the site where famed Sioux chief Crazy Horse met his fate.

America's largest man-made forest was planted in an effort to bring back the past.

This Great Plains museum pays tribute to both the prosperity and tragedy of the North American fur trade.

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

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

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

One of the largest private collections of fossils in the world.

The crumbling structure is a rare surviving relic of the area's bygone mining industry.