A stone pillar marking the location of the westernmost battle of the American Civil War only honors one side of the conflict.

A stone pillar commemorates the surrender of the extraordinary Apache leader.

This huge dam across the Colorado River caused an armed standoff between two U.S. states.

More than 300 years ago, a revolt at this Hopi pueblo shaped the future of the American Southwest.

A mysterious spirit totem at the edge of Navajo lands.

Walk through the actual strap iron cells and solitary chambers of Arizona Territory’s first prison.

Enormous piles of historically significant stones, dumped by Congress in a forest, and abandoned for 60 years.

A well-preserved Ancestral Puebloan ruin tucked beneath a desert cliff.

The remnants of an early American attempt at missile defense.

A crumbling hospital from the 1850s on Roosevelt Island.

Odd outsider art installations surround a Gold Rush-era ghost town.

A Saint Nicholas-themed ghost town in the Mojave desert.

The marker offers a rare chance to be in four U.S. states at once, though there's some controversy over its geographic accuracy.

In the middle of an extremely unforgiving and desolate high desert is the most secret military facility in the world.