Nogales is located in Santa Cruz County and it is the county seat of the county. The town lies south of Tucson along Interstate 19, near the United States/Mexico border. Nogales, Mexico, just south, is its sister city.

Nogales is the Spanish word for walnut trees. In the 1690s the Spanish established missions in this area inhabited by the Pima people. In 1821, Mexico ceded from Spain and the Nogales area became part of Mexico. In 1854, the Gadsden Purchase put Nogales into the United States. In 1880, Issac and Jacob Issacson founded Nogales with a border trading post. In 1882, the railroad arrived, assuring the town a place on the map.