Grinnell, IA has a population of 9,112 and is the 4,221st largest city in the United States. The population density is 1,655 per sq mi which is 2930% higher than the Iowa average and 1727% higher than the national average. The median age in Grinnell is 33 which is approximately 14% lower than the Iowa average of 38. In Grinnell, 44% of the population over 15 years of age are married, 93% speak English and 2% speak Spanish. 60% of Grinnell residents were born in Iowa, 33% were born out of state, 1% were born outside of the United States and 6% were foreign born.