The population in the census was 70,, up from 69, in the census. 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 , combining the communities of Alvarado and Decoto. Alvarado is a California Historical Landmark According to the United States Census Bureau , the city has a total area of 19 square miles 49 km 2 , all land with no bay frontage.
Hayward bounds the city to the north and Fremont and Newark to the south. About 4. Costanoans "coastal peoples" were the first inhabitants, living along Alameda and Dry Creeks. Shell mounds along the sloughs of Alameda Creek near the Alvarado sugar mill contained burial sites. Further east, Decoto was founded in as a railroad hub, hosting the first transcontinental railroad.
The plant was demolished in Union City is a former railroad and steel town with an extensive industrial heritage. The Alvarado and Decoto neighborhoods were both former railroad hubs and active railroad lines bisect both East End and the West Side of town.
Trains are a way of life in Union City and natives are accustomed to waiting for Amtrak and freight trains to cross while commuting. In the s, Alvarado and Decoto β the latter making up the eastern side of the town β were annexation targets of the nearby communities of Newark, Hayward, and what would become Fremont. On January 13, , they decided to incorporate into a single city, and named it after the Horners' original settlement, Union City.
