Grafton, IA has a population of 355 and is the 21,526th largest city in the United States. The population density is 1,092 per sq mi which is 1898% higher than the Iowa average and 1105% higher than the national average. The median age in Grafton is 44 which is approximately 16% higher than the Iowa average of 38. In Grafton, 64% of the population over 15 years of age are married, 99% speak English and 0% speak Spanish. 80% of Grafton residents were born in Iowa, 19% were born out of state, 0% were born outside of the United States and 0% were foreign born.