Fairmont City is a village in St. Clair and Madison counties, Illinois, United States.

The village limits extend west 3 miles (5 km) from the main portion of Fairmont City to touch the Mississippi River directly across from St. Louis.

[1] Fairmont City is built atop portions of the Cahokia Mounds, a UNESCO World Heritage Site.

In April 2016, the US Environmental Protection Agency added the Old American Zinc Fairmont City site to the National Priorities List following the Illinois EPA discovering high levels of lead, arsenic, cadmium and zinc in soil samples.

Collected soil samples from properties and alleyways showed residue of arsenic, cadmium and zinc.

[7] Fairmont City is 5 miles (8 km) east of the Gateway Arch of St. Louis.

This route once contained an accumulation of vintage, in situ roadside Americana advertising signage, most of which has not been removed or destroyed over time.