In 1873, Peter B. Bain filed the first formal claim to the land surrounding Agua Caliente Spring and, with Marion T. Beckwith, began a dairy cattle operation using cows brought north from Sonora. Bain built a house, outbuildings, and corrals at the spring, then sold Agua Caliente Rancho in 1875 to James P. Fuller of Hermosillo, Mexico, for $300. Fuller planted an orchard, constructed ditches and ponds for livestock and irrigation, and established a major cattle ranch by bringing nearly 1,200 head from Mexico. The one-room adobe ranch house, probably built by Bain, became the core of the main ranch house later expanded by other owners. During the 1870's, the ranch continued to provide water to the army and served as a stopping point for cattle drives in the eastern Tucson basin. By 1878, Fuller had also begun developing the hot springs, whose water was described in an assay as possessing tonic qualities of a high order, and Fuller's Hot Springs or Agua Caliente Resort soon opened. By the 1880's, Agua Caliente had become a destination hot springs resort that helped give Tucson a reputation as a healthful location, with cottages, hotel accommodations, a bathhouse, and an orchard of 3,000 trees. By 1882, the resort included several single-room adobe houses, a summer dining room made of ocotillo sticks, and a winter dining room with tight walls and a fireplace. Because of poor health, James Fuller conveyed the ranch to his sister, Eliza Jane Fuller Watson, who continued the resort. The resort era ended in 1897 when Philip H. Chambers purchased the ranch and thereafter charged admission at the gate. From then until the early 1950's, various owners operated Agua Caliente as a working cattle ranch, most notably Willard White, who used it as headquarters for his ranching interests. In the mid 1950's, the ranch was sold for planned subdivision and development, but those plans were never carried out, and in 1984 Pima County purchased the 100-acre property with assistance from Roy P. Drachman.