Marshalltown, IA has a population of 27,637 and is the 1,553rd largest city in the United States. The population density is 1,433 per sq mi which is 2524% higher than the Iowa average and 1482% higher than the national average. The median age in Marshalltown is 37 which is approximately 4% lower than the Iowa average of 38. In Marshalltown, 60% of the population over 15 years of age are married, 71% speak English and 24% speak Spanish. 64% of Marshalltown residents were born in Iowa, 17% were born out of state, 1% were born outside of the United States and 18% were foreign born.