At the time of its completion, it was the tallest dam in the world.

The high point on the 16th president's eponymous roadway is marked by a massive version of his head.

Population: 1.

A monument to the egos of two railroad magnates that fell into decline along with their careers.

Around half a million years ago, these magnificent columnar basalt cliffs were formed from cooling lava.

Surrounded by a hundred mile radius of billboards, Little America is a roadside attraction whose primary appeal is hospitality.

Miraculous tree that seems to sprout out of solid rock.

Long before guestbooks and hotels, frontier travelers signed their names on this rock face.

One of the smallest towns in the United States.

The only natural lake in the world that drains into both the Atlantic and Pacific Oceans.

This Yellowstone geyser may not shoot as high as the nearby Old Faithful, but it erupts for considerably longer.

An architect's childhood fantasy treehouse made real.

One of nature's most well-scheduled phenomenons resides in Wyoming's Yellowstone National Park.

One man's ambition created this psychedelic log home.

The largest hot spring in the United States is, as the name suggests, a stunning show of natural color.

A beautiful geyser under environmental threat.

The first declared National Monument in the United States.

The NBA player's elaborate former home is now a ghost of its old glory.

The palatial McDonald's that inspired Wesley Willis.

A display of magnificent stained glass windows is the first exhibit of its kind.

The company moved out of its sprawling headquarters, leaving plenty of traces behind.

A lone traffic cone perched on a ledge has remained unmoved since at least 2011, unofficially earning the status of a tiny Chicago landmark.

One of the last remaining French Colonial style churches, this centuries-old building was constructed using upright logs and no nails.

Meant for a railway that was never built because of the Great Chicago Fire, these piers still stand nearly 150 years after they were installed.