Union City is a city in the San Francisco Bay Area in Alameda County, California, United States 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. Incorporated in 1959, combining the communities of Alvarado and Decoto, the city has 70,000 residents and a very diverse population. Alvarado is a California Historical Landmark (#503). The city celebrated its 50th anniversary in 2009. The city, along with the cities of Fremont and Newark, make up the Tri-City Area to the south. The city of Hayward surrounds the city to the north.