San Bernardino Ranch

In 1884, John Horton Slaughter, a cowboy and lawman originally from Texas, purchased 65,000 acres (26,000 ha) from Perez's heirs for approximately $80,000. Two-thirds of his property lay in Mexico, with the remaining third in the Arizona Territory. There are ruins on the property now owned by the United States Fish and Wildlife Service where a Mormon employee of Slaughter's built a home (called the Mormon House) straddling the U.S.–Mexico border so he could keep a wife in the United States and a wife in Mexico. The home was two rooms, one on each side of the border, with a breezeway connecting them.

Slaughter was elected sheriff of Cochise County, Arizona in 1886, and served two terms through 1890. He became well known for restoring lawfulness in towns like Tombstone, Arizona after the infamous 1881 Gunfight at the OK Corral. The Tombstone jail was once known as the "Hotel de Slaughter". He helped tame the Arizona Territory, and was known to return from searching for outlaws with only their horses and equipment. Slaughter and his second wife, Viola Slaughter (born Cora Viola Howell), as well as her parents, Amazon and Mary Ann Howell, and Slaughter's children from his first marriage, Addie and Willie, lived at the ranch for many years. The 7.6 M_w  Sonora earthquake, centered in Bavispe, Sonora, destroyed the Howell residence on the property in 1887. The Howells managed the property until Slaughter finished his second term as sheriff. Slaughter had as many as 500 people living and working on the ranch, including many foster children. The most noteworthy of these was an Apache toddler, Apache May Slaughter, who was adopted by Slaughter after she was abandoned by her parents while Slaughter was tracking her band, who were responsible for killing white men in Arizona. Slaughter and the girl adored each other. She called Slaughter "Don Juan". She died from burns as her dress caught fire at age 6. She is buried in the cemetery on what is now the wildlife refuge.

Children were a large part of the ranch activities, and Slaughter loved children. There were enough children that the Slaughters built a schoolhouse, Slaughter School District No. 28. The children played in the natural artesian wells on the property and had picnics. Viola would bring the children ice cream from the icehouse. The kids loved swimming in the house pond, which was dammed by Slaughter for irrigation purposes. Slaughter loved technology. His was the first private home in southeastern Arizona to have a telephone. He owned six cars, yet never learned to drive.

From 1911 to 1920, the Slaughter Ranch Outpost for Camp Harry J. Jones in Douglas, Arizona was established on the ranch, on top of Mesa de la Avanzada overlooking the ranch house. Following the May 4, 1919 murder of Jesse Fisher by Manuel Garcia and Jose Perez, John and Viola moved to Douglas. John Slaughter died peacefully in his sleep on February 16, 1922. Viola sold the property around 1936 to a friend, Marion Williams.

In 1968 Paul and Helen Ramsower purchased the property. On August 7, 1964, the San Bernardino Ranch National Historic Landmark was entered on the National Register of Historic Places. The Ramsowers turned the ranch over to The Nature Conservancy in 1980. The buildings were purchased in 1983 by the Johnson Historical Museum of the Southwest and the United States Fish and Wildlife Service purchased most of the remaining property. Of the original acreage, 131 acres (53 ha) belong to the museum and the rest belongs to the San Bernardino National Wildlife Refuge. The refuge and ranch are home to the Yaqui Topminnow and Yaqui Chub, two endangered species of fish known to exist only in the valley.