San Mateo (săn mətā`ō), city (1990 pop. 85,486), San Mateo co., W Calif., on San Francisco Bay; inc. 1894. It is a commercial and retail center with some high-technology manufacturing. San Mateo, Spanish for St. Matthew, was named by a Spanish expedition in 1776. The area was a Mexican colony from 1822 to 1846. San Mateo's main growth dates from the start of railroad service in 1863. Refugees from the 1906 San Francisco earthquake greatly increased San Mateo's population. The city has a racetrack. The San Mateo–Hayward Bridge spans S San Francisco Bay from San Mateo and Foster City (W) to Hayward (E).