Clay, AL has a population of 9,659 and is the 4,040th largest city in the United States. The population density is 973 per sq mi which is 958% higher than the Alabama average and 974% higher than the national average. The median age in Clay is 45 which is approximately 15% higher than the Alabama average of 39. In Clay, 65% of the population over 15 years of age are married, 98% speak English and 1% speak Spanish. 77% of Clay residents were born in Alabama, 21% were born out of state, 1% were born outside of the United States and 1% were foreign born.