Montclair, CA has a population of 38,294 and is the 1,084th largest city in the United States. The population density is 6,941 per sq mi which is 2611% higher than the California average and 7561% higher than the national average. The median age in Montclair is 32 which is approximately 10% lower than the California average of 36. In Montclair, 45% of the population over 15 years of age are married, 38% speak English and 52% speak Spanish. 58% of Montclair residents were born in California, 7% were born out of state, 1% were born outside of the United States and 33% were foreign born.