This cannon dating to 1755 has stood guard at this suburban intersection since 1915.

This homestead was occupied by Union soldiers, who believed the owners were signaling Confederate forces.

At Brandy Station, Civil War soldiers left their mark on the battlefield and the walls of this small wooden house.

These trees are living witnesses to events that inspired poet Walt Whitman’s service during the American Civil War.

A relic of FDR's brief foray into utopian urban planning.

Baltimore's classic clock tower was once topped by a rotating, 20-ton medicine bottle.

Dogs, cats, horses, monkeys, frogs, and fish are laid to rest at the second-oldest pet cemetery in the U.S.

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

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

This abandoned sea fort has become an accidental bird sanctuary.

A little marble compass above George Washington's (empty) tomb in the Capitol marks where D.C.'s four quadrants intersect.

The iconic D.C. restaurant where the Cuban Missile Crisis was negotiated, now a Walgreens.

D.C. once had its own tiny rival to the New York Stock Exchange.

The 28,000-year-old specimen is remarkably intact.

A 1,100-ton train fell through the floor in 1953. Workers got it patched up in just 72 hours.

A small token of gratitude from freezing cold journalists who were given a warm haven while covering JFK's inauguration.

A derelict bit of infrastructure from the canal that once ran through D.C. is landlocked in the heart of the city.

One of the most influential presidents in U.S. history wanted only this plain, elegant monument as his lasting memorial.

This nine-story building is the oldest standing skyscraper in D.C.

There just so happens to be a court even higher than the U.S Supreme Court: a basketball court in the building itself.

Art deco landmark on the outskirts of Washington, D.C.

This stately mansion, built in 1787 by America's first Secretary of the Navy, is rumored to be one of the most haunted buildings in Washington, DC.

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