The smallest and oldest covered bridge in Delaware.

One of the few remaining covered bridges in Lancaster County.

This covered bridge was used by both Union and Confederate troops during the Battle of Gettysburg in 1863.

Little has changed in the way that this mill operates since the 18th-century.

A morbid secret lies hidden within the beautiful walls of the Boston Athenaeum.

This hidden treasure provides a charming access point along the south side of Baker Park.

An enormous warehouse filled with parade floats collected from over 50 years of patriotic celebrations.

In 1889, a small group of women began meeting to discuss literature, art, and other topics. Their every-other-week salon grew into a lending library that still exists today.

Inside this 150-year-old barn turned antique shop is a vast array of items for curios hunters.

Designated as an Underground Railroad research site.

The house where John Wilkes Booth conspired with his co-conspirators.

Mysterious installations bring levity and light to a sometimes stodgy city.

The house that Frank Lloyd Wright "(shook) out of his sleeve at will" at the age of 86.

Steepest flood safety railway in the entire world.

Behold the rickety wooden glory of the world's oldest operating roller coaster.

The oldest automobile museum in the United States.

A unique columnar residence built in the 19th century.

This tower commemorates the spot where George Washington hoisted the Grand Union flag.

This Massachusetts home was the first to have a telephone line and its own phone number: 1.

The site of Paul Revere's historic two lantern warning.

One of the oldest used bookstores in the U.S. has been selling antiquarian treasures since 1825.

Where you can hail your favorite fictional commanders-in-chief.

The wooden octagon in which Huckleberry Finn and A Connecticut Yankee were born can still be visited in upstate New York.

"Dark Sky Park" is heaven on Earth for astronomers, one of the rare U.S. locations with no artificial light pollution.