Part of the original Ute Reservation in 1868, Mancos was part of the San Juan Cession of 1873, and cattle ranchers began settling the Mancos Valley in the 1870s, providing cattle to the mining camps of the San Juan and La Plata ranges. Today, the boundary of the Ute Mountain Indian Reservation is located some south of town. At the time it was founded, Mancos served as the primary commercial trading center for eastern Montezuma County, rivaling the town of Dolores to the northwest. At that time, Cortez, now the county seat, was barely a bend in the wagon trail. In the 1890s, Mancos was platted and built as a stop along the Rio Grande Southern Railway built by Otto Mears - Colorado's southwestern railroad pathfinder, connecting Durango to the east, and the Telluride mining districts to the north, via Dolores. Ranchers in the Mancos Valley continued to provide beef, timber, and other agricultural products to the mining camps. Following this, Latter-day Saints colonists moved into the area and established farms and small communities such as Weber and Cherry Creek.