Nogales, Arizona is the gateway to the USA and sister city to Nogales, Sonora, MX. City of Nogales serves as both the economic capital and the county seat of Santa Cruz County, the smallest and southernmost of Arizona's counties. The city is mountainous with an elevation of 3,865 feet. Nogales, AZ was established in 1880 by Jacob and Isaac Isaacson, who built a trading post along the border. Two years later, Nogales, AZ was the site of the first rail connection between Mexico and the United States.