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

Historic home of America's sweetheart sharpshooter, Annie Oakley.

This one-room cabin where the young colonel slept during the French and Indian War.

The whole world in one water tank.

The antique hotel still has a jail in the basement, though the cockfighting ring is long gone.

Electronic inventions that resulted in products and systems we use every day are on display in this labor-of-love museum.

Meet some of the most prominent figures in Black history through life-sized wax models.

Remains of a historic fountain that was mysteriously lost in the demolition of a D.C. traffic circle.

This beautiful stone arch bridge wasn't even expected to stand for one day, but people have been crossing it for centuries.

Easter in Westminster may be the only time and place to behold Edgar Allen Poe made entirely of Marshmallow Peeps.

Live data is transmitted from the Atlantic coast to instantly recreate the ocean waves in this fountain at the NOAA headquarters.

Politicians, bureaucrats, and military officers gathered in this field near the Capitol to settle their disputes with blood.

The Forest Service's surprisingly sophisticated collection of wildfire prevention art features America's most beloved bear.

One of the oldest anatomical theaters in the U.S. still in use was once the site of an infamous cadaver riot.

A remarkable time capsule of American manufacturing deep in Maryland coal country.

A labor of love built by local hang-gliding enthusiasts, this ideal launch spot was outlawed by the authorities and has since been largely abandoned.

Rediscovered after a century, the father of the American Navy was reinterred in something dredged up from Davy Jones' Locker.

A pre-Industrial Age iron furnace and the site of a nearly-forgotten piece of Black history.

A haunting exhibit in a wildlife refuge center highlights threatened species and the conservation efforts needed to save them.

This former asylum for Black Americans is haunted by its history of violence and racism.

A remote horde of architectural treasures fit for Indiana Jones.

This fort down the Potomac from Washington, D.C. was once the only defensive fort protecting the capital.

Built by the patriotic residents of Boonsboro in a single day.

Brain collection and database that narrows the gap between man and animal.