The first community in what is now Union City was founded in 1850 by John and William Horner, also called "Union City," after their Sacramento River Steamship, "The Union." In 1854, it merged with the nearby community of New Haven (founded 1851) to form the town of Alvarado, named after the former Mexican governor, Juan Bautista Alvarado. Alvarado was the first county seat of Alameda County, a designation it soon lost in 1865 to San Leandro. Further east, the town of Decoto was founded in 1870 as a railroad hub, with the first Transcontinental Railroad running through it. Alvarado-Niles Road, one of the city's largest streets, connects the historical Fremont district of Niles with the historical Union City district of Alvarado.