The U.S. expansion westward following the Mexican-American War brought Spanish emigrants into this region. Naturally, the Native American Tribes did not appreciate the expansion that brought, what they considered, trespassers on their land. During the early 1860s, to defend against Indians, nearly 4,000 troops lived, worked, and socialized at the stone-and-adobe complex on the rugged outskirts of the San Mateo and Magdalena Mountains. Fort Craig was built as both a military fortress and a self-contained community and had everything from officers’ quarters, storehouses and horse stables; to a hospital, sutler’s store, blacksmith’s shop, carpentry shop, and more. Fort Craig's cottonwood-desert setting and rugged mountain outline were once a popular stationing request of troops. Officers’ children attended school, while enlisted men’s wives worked as laundresses for the community. Among the infantry and cavalry units who lived there were African American members of the Buffalo Soldiers who served within a segregated army that reflected the racial injustice of the nation they defended.
Fort Craig was the site of numerous campaigns against the Apache, Navajo and Comanche in order to both protect settlers from aggressive raids while also preserve the power of the United States and advance western expansion. Under the fort’s watchful eye, settlements like San Marcial to the north and Paraje to the south flourished as centers of the El Camino Real trade route. With the start of the Civil War in April of 1861, Fort Craig's location on the Royal Road led to it being the site of the first western battle of the Civil War.