As a part of Yankee-settled Northern Illinois, Carroll County became solidly Republican upon that party's formation in the 1850s. Of all the counties won by inaugural Republican Party presidential nominee John Charles Frémont in 1856, Carroll County was to maintain the longest unbroken string of supporting the GOP in subsequent elections. It would give a plurality to every subsequent Republican Presidential nominee up to George W. Bush in 2004, beating by three elections the second longest run of Indiana's Porter County which was to give a plurality to Bill Clinton in 1996.