Keystone, FL has a population of 23,850 and is the 1,834th largest city in the United States. The population density is 679 per sq mi which is 131% higher than the Florida average and 650% higher than the national average. The median age in Keystone is 43 which is approximately 4% higher than the Florida average of 42. In Keystone, 73% of the population over 15 years of age are married, 82% speak English and 10% speak Spanish. 37% of Keystone residents were born in Florida, 50% were born out of state, 2% were born outside of the United States and 11% were foreign born.