Mercer County Fact Sheet, Illinois State Archives. "Mercer County Fact Sheet". Archived from the original on October 23, 2007. Retrieved October 23, 2007.
naco.org
"Find a County". National Association of Counties. Retrieved June 7, 2011.
Mercer County Fact Sheet, Illinois State Archives. "Mercer County Fact Sheet". Archived from the original on October 23, 2007. Retrieved October 23, 2007.