Union City is a city in Alameda County, California, United States in the San Francisco Bay Area. It is located approximately 19 miles (31 km) south of Oakland, 30 miles (48 km) from San Francisco, and 20 miles (32 km) north of San Jose. It was incorporated in 1959, combining the communities of Alvarado and Decoto. The city has about 67,000 residents across a diverse population. Alvarado is a California Historical Landmark (#503). The city celebrated its 50th anniversary in 2009.