New Hartford, IA has a population of 621 and is the 18,223rd largest city in the United States. The population density is 1,245 per sq mi which is 2180% higher than the Iowa average and 1275% higher than the national average. The median age in New Hartford is 34 which is approximately 12% lower than the Iowa average of 38. In New Hartford, 71% of the population over 15 years of age are married, 100% speak English and 0% speak Spanish. 83% of New Hartford residents were born in Iowa, 17% were born out of state, 0% were born outside of the United States and 0% were foreign born.