Marengo, IA has a population of 2,927 and is the 8,932nd largest city in the United States. The population density is 1,408 per sq mi which is 2477% higher than the Iowa average and 1454% higher than the national average. The median age in Marengo is 36 which is approximately 5% lower than the Iowa average of 38. In Marengo, 54% of the population over 15 years of age are married, 94% speak English and 6% speak Spanish. 79% of Marengo residents were born in Iowa, 19% were born out of state, 0% were born outside of the United States and 2% were foreign born.