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

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

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

An isolated island home to one of the oldest English-speaking communities in the region and Maryland's state dessert.

A Civil War Museum with some notable medical antiques.

The final resting place of the tragic king and queen of the Jazz Age is tucked away in a small Maryland graveyard.

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

A model home in the Medical Examiner's Office in which grisly death scenes are staged to train forensic investigators.

This dig site outside D.C. is known for its exceptionally high density of baby dinosaur fossils and dinosaur eggs.

An FDR-era tuberculosis sanatorium has stood abandoned in the suburbs of the U.S. capital for over 30 years.

An astounding collection of medical specimens, including bits of President Lincoln.

The land is home to swimming ponies and a legendary 18th-century treasure.

La Monte Young and Marian Zazeela's "Dream House" will immerse you in an ever changing world of sound and light.

A church now sits over the site of one of the worst urban disasters of early 19th-century America.

At one of the nation’s longest-running professional theaters, the audience used to barter for tickets with produce and livestock.

An oft-overlooked, magically musical monolith that stands majestically between Arlington Cemetery and the Iwo Jima Memorial.

Though his role as the inventor of baseball may be up for debate, fans still festoon Doubleday's grave with baseballs.

This small pedestal marks the spot of the first lot of land sold in Alexandria, Virginia in 1749.

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

The location where the American Revolution ended.

This church is known as "The Home Church of George Washington and George Mason."

A 100-foot metal tower and swinging bridge that provides stunning views of mountains in five states.

The Pentagon is so large that it was planned like a city, complete with internal highway infrastructure.

The system of air guns are fired off remotely to scare any trespassing avians.