Fort Cronkhite, a former World War II military post located in the Marin Headlands, is the park's best preserved example of a World War II "mobilization post". Starting in 1939, the U.S. Army built hundreds of similar wood-frame, temporary military posts around the country for the wartime training and housing of soldiers. By some estimates, more than 100,000 of these buildings were constructed between 1940 and 1945.
The buildings at Fort Cronkhite, completed in 1941, are typical of thousands of wartime barracks, mess halls, supply buildings once constructed from coast to coast. Fort Cronkhite originally housed hundreds of Coast Artillery soldiers assigned to the army's sprawling Harbor Defenses of San Francisco. Their mission was to protect San Francisco Bay against enemy attack and during World War II, the soldiers manned gun batteries, radar sites, and other fortifications on the high ridges overlooking the fort.