|Williamson County Illinois Cities/Towns -
Bush, Cambria, Carterville, Colp, Corinth, Crainville, Creal Springs, Energy, Freeman Spur, Herrin, Hurst, Johnston City, Marion (County Seat), Pittsburg, Spillertown
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Williamson County is a county located in the U.S. state of Illinois. As of 2016, the population was 67,560. Its county seat is Marion.
Williamson County was formed on February 28, 1839. It was named for Williamson County, Tennessee.