 First established after the end of the Mexican–American War (1848), the fort was originally located in the bottoms near the Colorado River, less than a mile below the mouth of the Gila River.It was constructed to defend the newly settled community of Yuma, New Mexico Territory, located on the other side of the Colorado River, and the nearby Mexican border.In March 1851 the post was moved to a small elevation on the Colorado's west bank.