A traveling postal dog covered 48 states and more than 140,000 miles, and he lives on as taxidermy, patched up with a rabbit's foot and a pig's ear.

The remains of Martha, the last known passenger pigeon, serve as a tool to educate about conservation.

Sit where JFK proposed to Jackie or where Nixon dined on meatloaf at this storied pub.

An overlooked oasis of quiet on the grounds of Washington's monumental basilica.

A clone of a cloned tree that was so important it allegedly had its own guards.

Housing the National Women's Party since 1929, this historic house is now a monument to the fight for gender equality.

Seemingly unremarkable items like empty sushi trays, chef hats, and freshness stickers are being preserved so future generations can look back on this beloved cultural import.

An easily overlooked memorial to a Ukrainian famine-genocide that killed over 4 million people.

These recently uncovered walls are all that's left of Washington, D.C's first defense contractor.

Perhaps the most scandalous statue of America's first president.

A hoard of sky catalogs, astrophysical journals, even the works of Galileo and Copernicus.

A celebrity from the late Cretaceous period.

A haunting tribute to pioneering photographer Clover Adams.

The hidden offices underneath Memorial Bridge have been locked up since 1976.

A computer bug so primitive it was an actual insect.

A brass plaque dedicated to a convicted cannibal hangs in the National Press Club, and that's not even the craziest part of the story.

Cold War intelligence agents monitored communist embassies from an attic in a former pigeon coop.

This leafy estate is worth $18 million and is so grand it has two mailing addresses.

An obscure public service from the U.S. government that redeems burnt, moldy, and soiled old greenbacks.

There's a crumbling old mansion inside the Smithsonian National Zoo.

The famous abolitionist’s preserved estate is one of Washington's finest monuments to its great Black citizens.

The most decorated dog of World War I is preserved in the Smithsonian.

The actual model from the original "Star Trek" series is now on display at the National Air and Space Museum.

Government testing at the asylum briefly explored using marijuana as a "truth serum" on Nazi prisoners of war.