Seacliff, CA has a population of 3,364 and is the 8,240th largest city in the United States. The population density is 4,388 per sq mi which is 1788% higher than the California average and 4744% higher than the national average. The median age in Seacliff is 46 which is approximately 27% higher than the California average of 36. In Seacliff, 55% of the population over 15 years of age are married, 88% speak English and 8% speak Spanish. 69% of Seacliff residents were born in California, 23% were born out of state, 1% were born outside of the United States and 7% were foreign born.