Once one of the world's great cities, Cahokia was a place of religious worship, trade and mass human sacrifice before being mysteriously abandoned.

The Old Courthouse takes visitors on a captivating trip through St. Louis' timeline.

Giant works of art interspersed throughout meadows and woodlands offer a new discovery at every turn.

One day a year it is legal to jump off of this astoundingly tall bridge that spans an Appalachian gorge.

The Man In Black grew up in a large agrarian community established by the federal government in the Great Depression.

The hotel where Martin Luther King Jr. was shot is now a museum dedicated to his work.

Walk the whole Mississippi River!

The stone marker that Mason and Dixon placed at the eastern end of the famous north-south border they surveyed.

The highest point in South Carolina was once owned by an energy company that neglected it but now the state is taking it back.

Gnarled canopies of pink and purple wildflowers arch over the trail to the summit.

The artwork commemorates the many ways 20th-century people perished while on the clock.

So many migrating birds roost on the bridge, it has a special summer speed limit.

The lesser-known lost colony of Roanoke was a safe haven for formerly enslaved people during the Civil War.

This shifting North Carolina sand dune is an odd little desert surrounded by oceanic forest life.

Down the road from where the Wright brothers lifted off is another flight tribute practically hidden from sight in the woods.

The Cadillac Ranch for monster truck aficionados.

This bright yellow relic is the final survivor of a short burst of seashell-shaped petrol pumps.

The highest point in Iowa, while not that impressive to mountain states, has earned its own monuments.

Less a museum than a bizarre fantasy world created by artists and engineers.

A smaller model of the Da Vinci sculpture that took 500 years to come to life.

A human attendant once directed car traffic from this structure before automated stoplights.

The only geyser in the state of Pennsylvania is caused by pressure from an abandoned coal mine outside of the ghost town Centralia.

This palatial botanical garden is home to one of the largest pipe organs ever installed in a private residence, and a piece of Wood's cycad.

While many places make the claim, the Library of Congress says this restaurant is the birthplace of the hamburger.