New Jersey's last historic covered bridge was rebuilt from pieces of the original 19th-century structure.

A monument marks the location of the first successful steamboat demonstration.

The 44,000-ton aircraft carrier was purposely sunk to create an artificial reef teeming with life.

For decades, this waterfall remained hidden because of an artificial dam.

Memorializing an American tragedy of massive proportions.

The tomb was guarded by soldiers from both sides of the war, and some left their initials carved in the brick.

A bas relief commemorates the "Nuns of the Battlefield" who cared for soldiers on both sides of the conflict.

A collection of huge, site-specific sculptures sitting in the Montana woods.

The former estate of the Guggenheims, part of the opulent Gold Coast that inspired the Great Gatsby.

Pulled from the rubble of one of the worst modern tragedies, a steel crossbeam became a symbol of hope for New Yorkers.

Before founding the American Red Cross, Clara Barton had a tremendous humanitarian impact by locating thousands of missing soldiers.

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

This concrete ship has had four careers - World War I tanker, floating amusement park, fishing pier, and artificial reef.

"Where the ducks walk on fish."

The maritime museum that boasts the largest nautical library in the western hemisphere.

A Biblically-based Natural History Museum.

A historic freight system that found the true gold rush is in tourism.

The largest known open fault in the United States is basically a giant natural refrigerator.

The preamble to the U.S. Constitution written entirely from vanity license plates hangs in the Smithsonian museum.

A lighthouse on a diminutive island was one of the first of its kind to guide seamen home.

Get up close and personal with these majestic fish.

Hidden beneath the waters of Lake Michigan rests a perfectly intact ship from the early 1900s.

A preserved 18th century homestead in Western Pennsylvania marks the spot where the Whiskey Rebellion began.

A tiny monument to the unsuccessful attempt by Thomas Jefferson to place the prime meridian in Washington.