Grantfork, IL has a population of 360 and is the 21,450th largest city in the United States. The population density is 1,216 per sq mi which is 447% higher than the Illinois average and 1242% higher than the national average. The median age in Grantfork is 34 which is approximately 10% lower than the Illinois average of 37. In Grantfork, 75% of the population over 15 years of age are married, 98% speak English and 2% speak Spanish. 80% of Grantfork residents were born in Illinois, 19% were born out of state, 1% were born outside of the United States and 1% were foreign born.