Seaside, CA has a population of 34,120 and is the 1,241st largest city in the United States. The population density is 3,693 per sq mi which is 1489% higher than the California average and 3976% higher than the national average. The median age in Seaside is 31 which is approximately 13% lower than the California average of 36. In Seaside, 50% of the population over 15 years of age are married, 52% speak English and 36% speak Spanish. 49% of Seaside residents were born in California, 19% were born out of state, 2% were born outside of the United States and 29% were foreign born.