Fort Belknap, located near Newcastle, Texas, was established in 1851 by brevet Brigadier William G. Belknap to protect the Texas frontier against raids by the Kiowa and Comanche. It was the northernmost fort in a line from the Rio Grande to the Red River. The fort functioned as a base of operations rather than as a fortified point, and it became the center of a substantial network of roads, including the Butterfield Overland Mail.
Notable officers who were stationed at Fort Belknap included Captain Randolph B. Marcy and Lieutenant George B. McClellan, who together explored the Canadian River and found the headwaters of the Red River.
Prior to the outbreak of the American Civil War the post was abandoned, partly as a pullback of Federal troops to the north, and partly due to the fort's unreliable water supply. The fort was briefly re-occupied in 1867, then abandoned for the last time.
The fort was gradually dismantled for building materials, so that by 1936 only the magazine and part of the cornhouse remained. Beginning with the Texas Centennial, portions of the fort were rebuilt and restored. mostly on their original foundations. The fort is home to the Fort Belknap Archives, which houses records from North Texas.