Centralia is a town located in Marion, Washington, Clinton, and Jefferson Counties in the U.S. state of Illinois. The town was founded because it was the point where the two original branches of the Illinois Central Railroad, built in 1853, converged. The town is named for the railroad. The current mayor is Tom Ashby. According to the United States Census Bureau, the city has a total area of 7.6 square miles (20km2), of which, 7.5 square miles (19km2) of it is land and 0.1 square miles (0.26km2) of it (1.83%) is water.