- Empire Ranch is a working cattle ranch in southeastern Pima County - Established in 1876, the ranch is located in the 45,000-acre Las Cienegas Conservation Area, north of Sonoita - The ranch was started by Walter L Vail and became the largest ranching operation in Arizona - 1976: placed on the National Register of Historic Places - Located between Vail and Sonoita along Arizona Highway 83 - The ranch is part of a borderland between the Sonoran and Chihuahuan Deserts of southern Arizona Website ==> www.blm.gov/visit/historic-empire-ranch Map