Newark is a city in Alameda County, California, United States. It was incorporated as a city in September 1955. Newark is an enclave, surrounded by the city of Fremont. The three cities of Newark, Fremont, and Union City make up the Tri-City Area. Newark's population was 47,529 at the 2020 census making it the third largest city in the US named Newark after Newark, New Jersey, and Newark, Ohio.