Armstrong, IA has a population of 898 and is the 15,815th largest city in the United States. The population density is 1,026 per sq mi which is 1777% higher than the Iowa average and 1032% higher than the national average. The median age in Armstrong is 48 which is approximately 27% higher than the Iowa average of 38. In Armstrong, 64% of the population over 15 years of age are married, 98% speak English and 2% speak Spanish. 59% of Armstrong residents were born in Iowa, 40% were born out of state, 0% were born outside of the United States and 1% were foreign born.