Grundy Center, IA has a population of 2,705 and is the 9,358th largest city in the United States. The population density is 1,047 per sq mi which is 1736% higher than the Iowa average and 1055% higher than the national average. The median age in Grundy Center is 42 which is approximately 11% higher than the Iowa average of 38. In Grundy Center, 65% of the population over 15 years of age are married, 98% speak English and 0% speak Spanish. 89% of Grundy Center residents were born in Iowa, 11% were born out of state, 0% were born outside of the United States and 0% were foreign born.