Knoxville, IA has a population of 7,236 and is the 5,061st largest city in the United States. The population density is 1,564 per sq mi which is 2763% higher than the Iowa average and 1626% higher than the national average. The median age in Knoxville is 40 which is approximately 5% higher than the Iowa average of 38. In Knoxville, 56% of the population over 15 years of age are married, 96% speak English and 3% speak Spanish. 78% of Knoxville residents were born in Iowa, 20% were born out of state, 0% were born outside of the United States and 2% were foreign born.