Killen, AL has a population of 1,129 and is the 14,404th largest city in the United States. The population density is 558 per sq mi which is 506% higher than the Alabama average and 516% higher than the national average. The median age in Killen is 38 which is approximately 1% lower than the Alabama average of 39. In Killen, 65% of the population over 15 years of age are married, 95% speak English and 5% speak Spanish. 72% of Killen residents were born in Alabama, 27% were born out of state, 0% were born outside of the United States and 2% were foreign born.