Fort Belknap functioned as a U.S. Army frontier post established in 1851 south of present Newcastle, serving as the northern anchor of a chain of forts guarding the upper Brazos frontier and the settlers moving into it. As a garrison post it housed rotating companies of cavalry and infantry who patrolled against raiding parties and, on occasion, mounted expeditions as far north as Kansas. The fort became a hub of frontier infrastructure, with roads radiating outward in several directions, including a branch of the Butterfield Overland Mail route linking St. Louis and San Francisco, and its presence encouraged settlement and the organization of surrounding counties. Federal troops abandoned the post in 1861, it saw brief Union reoccupation in 1867, and it was permanently abandoned that September once Fort Griffin assumed its strategic role farther northwest. Today Fort Belknap operates as a restored historic and cultural site rather than an active military installation. Following restoration work during the Texas Centennial era, the property functions as a museum and recreational center drawing tens of thousands of visitors annually, with several original and reconstructed stone buildings open to the public. It is maintained by the Fort Belknap Society in cooperation with the Young County Commissioners Court, and it houses archival collections documenting the history of North Texas frontier settlement, making it both a heritage tourism destination and a local historical resource.