Mercer County, Illinois
Lat/Long: 41.2000, -90.7500
On January 13, 1825, the Illinois General Assembly founded Mercer County. Founders named the county for Hugh Mercer, a Revolutionary War general and physician who died in the Battle of Princeton. In January 1835, the General Assembly organized the county, naming New Boston the temporary county seat. New Boston (1835-37), Millersburg (1837-47), and Keithsburg (1847-57) hosted the County Commissioners' Court and county courts until 1857, when voters made Aledo the permanent county seat.
"An Act Forming New Counties Out of the Counties of Pike and Fulton, and the Attached Parts Thereof," 13 January 1825, Laws of Illinois (1825), 92-96; Newton Bateman and Paul Selby, eds., Historical Encyclopedia of Illinois and History of Mercer County, ed. by William A. Lorimer (Chicago: Munsell, 1903), 634, 636-37; An Act to Organize the County of Mercer.