Grantfork is a village in Madison County, Illinois, United States. The population was 337 as of the 2010 census.
Grantfork is located at 38°49′50″N 89°39′58″W / 38.830427°N 89.666212°W / 38.830427; -89.666212.
According to the 2010 census, Grantfork has a total area of 0.308 square miles (0.80 km), of which 0.3 square miles (0.78 km) (or 97.4%) is land and 0.008 square miles (0.02 km) (or 2.6%) is water.
As of the census of 2000, there were 254 people, 101 households, and 67 families residing in the village. The population density was 1,112.1 people per square mile (426.4/km²). There were 103 housing units at an average density of 451.0 per square mile (172.9/km²). The racial makeup of the village was 99.21% White, 0.39% Native American, and 0.39% from two or more races. Hispanic or Latino of any race were 0.39% of the population.
There were 101 households out of which 37.6% had children under the age of 18 living with them, 50.5% were married couples living together, 8.9% had a female householder with no husband present, and 32.7% were non-families. 29.7% of all households were made up of individuals and 8.9% had someone living alone who was 65 years of age or older. The average household size was 2.51 and the average family size was 3.09.
In the village, the population was spread out with 29.1% under the age of 18, 7.1% from 18 to 24, 32.3% from 25 to 44, 22.4% from 45 to 64, and 9.1% who were 65 years of age or older. The median age was 36 years. For every 100 females, there were 92.4 males. For every 100 females age 18 and over, there were 97.8 males.
The median income for a household in the village was $42,917, and the median income for a family was $48,750. Males had a median income of $36,563 versus $21,458 for females. The per capita income for the village was $17,415. About 3.1% of families and 4.4% of the population were below the poverty line, including none of those under the age of eighteen or sixty five or over.