Mount Vernon, IA has a population of 4,487 and is the 6,934th largest city in the United States. The population density is 1,285 per sq mi which is 2252% higher than the Iowa average and 1318% higher than the national average. The median age in Mount Vernon is 23 which is approximately 40% lower than the Iowa average of 38. In Mount Vernon, 44% of the population over 15 years of age are married, 97% speak English and 2% speak Spanish. 53% of Mount Vernon residents were born in Iowa, 43% were born out of state, 2% were born outside of the United States and 2% were foreign born.