Wikipedia: Natl Historic Landmarks in Arizona: Fort Bowie Natl Historic Site

A military fort built just before the American Civil War to defend San Francisco Bay against hostile warships.

Last surviving Titan II missile launch facility; inactive.

A major crossroads for Alta California as well as the Westward expansion of the United States. It has several archaeological and historical sites, shared with Arizona across the Colorado River, including Fort Yuma and other state parks.

Site of a Native American fort.

An image of the Fort Pierre Chouteau Site.

Fort Phil Kearny was an outpost of the United States Army that existed in the late 1860s in present-day northeastern Wyoming along the Bozeman Trail.

An image of the Fort Pulaski National Monument.

An image of the Fort Frederica National Monument.

Archaeological site at first permanent Dutch settlement in New Netherland.

Work site of C. Hart Merriam, path-breaking eco-biologist.