Old Alvarado is a former settlement in and former county seat of Alameda County, California, now annexed to Union City. It was located 5mi north-northwest of downtown Newark.In 1851, Henry C. Smith founded the town of New Haven, named after his father's home town of New Haven, Connecticut. In 1853, the town amalgamated with a nearby town called Alvarado, and became the county of seat of the newly formed Alameda County. Alvarado was named for Juan Alvarado, Mexican Governor of California from 1836 to 1842. The first post office opened in 1853.On January 13, 1959, Alvarado and Decoto voted to incorporate as the new City of Union City, California.
