This house was once the location of Frelinghuysen University.

This rowhouse doubles as one of the most photographed spots in the nation's capital.

Once the largest trading firm of enslaved people in the U.S., this building is now a museum that preserves Alexandria's dark past.

Where three rails and three centuries of transportation meet.

In an effort to escape the horrors of slavery, one man mailed himself to freedom.

The only U.S. Senator to die on the field of battle is buried in San Francisco but memorialized at Balls Bluff Regional Park.

Extraordinary objects lurk in this quintessential regional museum.

These buildings are a poignant reminder of the thousands of horses and mules who passed through this area of the Shenandoah Valley on their way to war.

This sprawling farm was once a Cold War-era hideaway for the nation's top diplomats.

This propitious plastic porcine has been petitioning park visitors to pick up after themselves for more than 50 years.

The location where the famed author and abolitionist began his journey to freedom.

The monument's pointy aluminum tip has been melted down by repeated lightning strikes.

The oldest building in the District of Columbia was preserved because of a mistaken connection to George Washington.

This fertility idol of questionable authenticity inspired an iconic Indiana Jones artifact.

This small hilltop church weaves the urban history of Washington, D.C. with the national history of the United States.

People escaping slavery may have hidden inside a corpse vault.

A terrace reminiscent of Rome's Spanish Steps is tucked away in a little park in Washington, D.C.

The sculptor was instructed to add “stallion attributes” to the general's bronze mare.

One of the last mosaic tile facades found in the city.

Fittingly, America's museum of architecture is itself a magnificently designed old building.

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

The childhood home of the Sultan of Swat is just a line drive away from Oriole Park at Camden Yards.

The wooded estate of the Forest Service employee responsible for D.C.’s cherry blossom trees.

A surprising, but overlooked example of geology in the middle of the nation’s capital.