Belmont (bĕlˈmŏnt) [key]. 1 City (1990 pop. 24,127), San Mateo co., W Calif., a residential suburb midway between San Francisco and San Jose; laid out 1851, inc. 1926. There is light manufacturing, and the College of Notre Dame (est. 1851) is there. 2 Town (1990 pop. 24,720), Middlesex co., E Mass., a residential suburb of Boston; settled 1636, inc. 1859.