Oklahoma City, OK has a population of 620,015 and is the 28th largest city in the United States. The population density is 1,023 per sq mi which is 1774% higher than the Oklahoma average and 1029% higher than the national average. The median age in Oklahoma City is 34 which is approximately 6% lower than the Oklahoma average of 36. In Oklahoma City, 53% of the population over 15 years of age are married, 80% speak English and 15% speak Spanish. 58% of Oklahoma City residents were born in Oklahoma, 29% were born out of state, 1% were born outside of the United States and 12% were foreign born.