Martinez, CA has a population of 37,544 and is the 1,109th largest city in the United States. The population density is 2,972 per sq mi which is 1179% higher than the California average and 3181% higher than the national average. The median age in Martinez is 44 which is approximately 22% higher than the California average of 36. In Martinez, 56% of the population over 15 years of age are married, 85% speak English and 7% speak Spanish. 66% of Martinez residents were born in California, 21% were born out of state, 1% were born outside of the United States and 11% were foreign born.