Gibson County was named for John Gibson, an officer in the French and Indian War and the Revolutionary War. Gibson was Secretary of the Indiana Territory, serving as acting Governor on two occasions. The two counties of Gibson County and Warrick County, separated by Rector's Base Line, were formed March 9, 1813. Gibson County was organized on April 1, 1813 while Warrick County was organized on April 30, meaning that both territories fell under Gibson County for that nearly two-month period. Gibson County occupied everything from the Wabash River and from the White River's extension to the Paoli Base Line down the 2d Principal Meridian to the Rector's Base Line. The area south of this line became Warrick County, which covered the area from the 2d Principal Meridian west to the Wabash River and down the Wabash River and with meanders up the Ohio River back to the 2d Principal Meridian (which had separated Knox County from Harrison County, Indiana Territory). Orange County, Spencer County, Pike County, Dubois County, and Crawford County all came from the roughly area occupied by the original Gibson County, as well as small portions of Lawrence County, Perry County, Posey County, the current Warrick County, and Vanderburgh County.