Allerton, IA has a population of 549 and is the 18,992nd largest city in the United States. The population density is 482 per sq mi which is 783% higher than the Iowa average and 432% higher than the national average. The median age in Allerton is 34 which is approximately 10% lower than the Iowa average of 38. In Allerton, 61% of the population over 15 years of age are married, 99% speak English and 0% speak Spanish. 65% of Allerton residents were born in Iowa, 34% were born out of state, 1% were born outside of the United States and 1% were foreign born.