In 1863, Fort Bascom was built along the Canadian River in the Eroded Plains of Territorial New Mexico. Its unique location placed it between the Comanches of Texas and the Comancheros of the Sangre de Cristo Mountains. This post was situated within Comanchería during the height of the United States Army's war against the Southern Plains Indians, yet it has garnered little attention. This study broadens the scholarly understanding of how the United States Army gained control of the Southwest by examining the role Fort Bascom played in this mission. This includes an exploration of the Canadian River Valley environment, an examination of the economic relationship that existed between the Southern Plains Indians and the mountain people of New Mexico, and an account of the daily life of soldiers posted to Fort Bascom. This dissertation thus provides an environmental and cultural history of the Canadian River Valley in New Mexico, a social history of the men stationed at Fort Bascom, and proof that the post played a key role in the Army's efforts to gain control of the Southern Plains Indians. This study argues that Fort Bascom should be recognized as Texas' northern-most frontier fort. Its men were closer to the Comanche homeland than any Texas post of the period. Its records clearly show that the Army used Fort Bascom as a key forward base of operations against Comanches and Kiowas. An examination of Bascom's post returns, daily patrols, and major expeditions allows its history to provide a useful perspective on the nineteenth-century American Southwest.