 From 1870 on, the Army used the area for forts such as Fort Cronkhite, coastal batteries such as those that protected the San Francisco Bay during WW II, and missile sites, such as the 280 that occupied the area during the Cold War.While in the Marin Headlands, the Army planted a lot of trees, so many that today the non-native, invasive species that occupy the Headlands threaten the habitat of the Mission blue butterfly.The habitat protection program seeks to root out these species from selected areas of the Marin Headlands.