Sioux City, IA has a population of 82,666 and is the 416th largest city in the United States. The population density is 1,414 per sq mi which is 2489% higher than the Iowa average and 1461% higher than the national average. The median age in Sioux City is 34 which is approximately 10% lower than the Iowa average of 38. In Sioux City, 53% of the population over 15 years of age are married, 82% speak English and 14% speak Spanish. 66% of Sioux City residents were born in Iowa, 23% were born out of state, 1% were born outside of the United States and 10% were foreign born.