Newton, IA has a population of 15,090 and is the 2,818th largest city in the United States. The population density is 1,340 per sq mi which is 2353% higher than the Iowa average and 1379% higher than the national average. The median age in Newton is 42 which is approximately 10% higher than the Iowa average of 38. In Newton, 57% of the population over 15 years of age are married, 98% speak English and 1% speak Spanish. 81% of Newton residents were born in Iowa, 17% were born out of state, 0% were born outside of the United States and 1% were foreign born.