Fort Belknap, a United States Army post three miles south of Newcastle in Young County, was founded on June 24, 1851, at the site of present Newcastle by Bvt. Brig. Gen. William G. Belknap. After the commanding officer, Capt. C. L. Stephenson, Fifth Infantry, found no water in shafts dug sixty-six feet deep at the location of the water tower now in Newcastle, he moved the fort two miles south, where adequate water was found in springs by the Brazos River. The present well was dug in 1857 under the direction of Capt. Gabriel R. Paul of the Seventh Infantry. The first buildings were jacals. Some were later replaced with stone.
Fort Belknap was a four-company post. Among the companies stationed there during its existence were some from the Fifth United States Infantry, the Second United States Dragoons, the Seventh United States Infantry, the Second United States Cavalry, and the Sixth United States Cavalry. Among the commanding officers were Col. Gustavus Loomis, Maj. Enoch Steen, Captain Paul, Maj. George H. Thomas, Maj. Samuel Henry Starr, Lt. Col. Samuel Davis Sturgis, and Capt. Richard W. Johnson.
Fort Belknap was the northern anchor of a chain of forts founded to protect the Texas frontier from the Red River to the Rio Grande. It was a post without defensive works. From it troops pursued raiding bands of Indians, and on occasion mounted expeditions from the fort carried the war to the enemy on the plains as far north as Kansas. The fort gave confidence to citizens, who came in such numbers that surrounding counties were organized. Fort Belknap became the hub of a network of roads stretching in every direction; the most notable of these was the Butterfield Overland Mail route from St. Louis to San Francisco.
In early 1861, believing that war was imminent, Gen. David E. Twiggs ordered Col. William H. Emory to gather all federal troops and move them north to Fort Leavenworth. On February 9, 1861, General Twiggs, in San Antonio, surrendered all United States forts and military equipment in Texas. Although it was abandoned before the Civil War, the fort was occupied from time to time by state troops of the Frontier Regiment under Col. James M. Norris. Major Starr, with troops of the Sixth United States Cavalry, reoccupied Fort Belknap on April 28, 1867. When Fort Griffin was founded in Shackelford County, Fort Belknap was abandoned for the last time, in September of 1867.
During the Texas Centennial, Senator Benjamin G. Oneal and local citizens restored and rebuilt some of the buildings. During the 1970s the Fort Belknap Archives, with some assistance from the Young County Commissioners Court, rebuilt Infantry Quarters Number Four to house the records of North Texas. Since its restoration Fort Belknap has become a cultural and recreational center. Senator Oneal and others organized the Fort Belknap Society to supervise the maintenance of the fort. The Young County Commissioners Court supports it financially. Professional and learned societies, as well as family groups, use the facilities, and around 30,000 visitors register their attendance annually.