A star fort along the C&O Canal in western Maryland that protected America in three wars.

A massive tribute to this small county's top agricultural product.

The second building of its name to occupy this location might be the finest flatiron building in San Francisco.

One time home to turn of the century explosives, now hidden under the Bay Bridge.

The key to turning shifting dunes into the green oasis of Golden Gate Park.

This private residence was the template for one of the most beloved television homes of all time.

The seawater playground of gilded-era San Francisco burned to the ground in 1966.

Bring your own cardboard to the slippery slopes of concrete hidden in a neighborhood park.

The uniquely-designed winter home and sculpture studio of Anna and Archer Huntington.

This former tuberculosis research hospital endeavored to cure the dreaded disease with fresh air and positive attitudes.

The last holdout of a pre-Civil War rebel who took the matter of slavery into his own hands.

Berkeley Springs State Park boasts the nation's only monument commemorating presidential bathing.

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

A particularly creepy abandoned hospital that sparks interest for lovers of the supernatural.

A sacred site for Native Americans surveyed by George Washington and owned by both King George III and Thomas Jefferson.

Maryland's first (and last standing) toll house on America's first federal road established the state as the "Gateway to the West."

An icon among Florida's pre-Disney tourist attractions, just west of Orlando.

An 18th-century Spanish watchtower made entirely of seashell and concrete.

A luxurious 1880s hotel with its fair share of Tiffany stained glass, Edison electricity, and of course, ghosts.

In Florida, these naughty monkeys live on their own mini-monkey Alcatraz.

A tribute to Ponce de Leon's supposed quest for eternal youth.

The highest point in North Carolina and the United States east of the Mississippi River, Mount Mitchell is named after argumentative explorer Elisha Mitchell.

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

Meet manatees face-to-face at this zoo for native species.