Fairmont City is a village in St. Clair County, Illinois, United States. It is located only few miles away from St. Louis, the second largest city in Missouri.

According to the United States Census Bureau of 2000, Fairmont City has a population of just over 2,400 people. The village has a total area of 2.4 square miles.

The racial demographics of Fairmont City are 66.54% White, 1.23% African American, 0.94% Native American, 0.08% Asian, 27.50% from other races, and 3.69% from two or more races. Hispanic or Latino of any race make up more than half of the population.

Fairmont City has over 850 households. The median income for a household in the village is $27,070, and the median income for a family is $31,296.

St. Clair County is located in southern Illinois and is surrounded seven other counties, including two counties from Missouri. The county is located only 15 miles away from St. Louis, Missouri.

According to the U.S. Census Bureau of 2006, St. Clair County has a population of more than 260,000 people. The county has a total area of 674 square miles with 10 square miles of water.

St. Clair County is divided into 17 townships, which have dozens of cities and towns The county seat is Belleville.