Clay, CA has a population of 1,209 and is the 13,984th largest city in the United States. The population density is 179 per sq mi which is 23% lower than the California average and 98% higher than the national average. The median age in Clay is 48 which is approximately 34% higher than the California average of 36. In Clay, 63% of the population over 15 years of age are married, 77% speak English and 21% speak Spanish. 70% of Clay residents were born in California, 12% were born out of state, 0% were born outside of the United States and 18% were foreign born.