Harco is an unincorporated community in Saline County, Illinois, United States.

The Harrisburg Colliery Coal Company Mine was sunk in November 1916, in the center of section 27, township 8, range 5, Saline County, Illinois, and the town of Harco soon grew up around it.

The houses were prefabricated Sears Catalog Homes shipped by railroad to the mine and then delivered to the building sites by wagon.

When the Harco mine closed in April 1951, families living in the company houses were given evacuation notices.

The Harco post office was established on November 21, 1917, and Thomas Hoffman was its first postmaster.

A larger framed two-room school was built and ready in the fall of 1917.

Several years later it burned down, and a large two-story brick five-room school building was built.

In May 2007 a group of 60 Amish men, women and children moved from Wisconsin to Saline County, Illinois where they purchased almost 800 acres (3.2 km2) of land to farm near Harco.