A Very Brief History of Boone County, Illinois
Boone County, Illinois, was organized from Winnebago County on March 3, 1836, being named in honor of Kentucky's pioneer, Daniel Boone. However, its present boundaries were not gained until May 4, 1843, when a mile-wide strip was annexed to the western border from Winnebago County.
Boone County is bordered on the north by Wisconsin (Rock and Walworth Counties), on the south by DeKalb County, on the east by McHenry County, and on the west by Winnebago County. In 1850, there were eight townships: Belvidere, Benton (previously Fairfield and then Flora), Boone, Bonus, Caledonia, Leroy (previously Beaver), Manchester and Ohio (later renamed as Spring). Poplar Grove township was eventually created from parts of Boone and Caledonia townships.
Boone County is the smallest of the "northern tier" of counties, having an area of only 290 square miles. Before agriculture was introduced, its surface was chiefly rolling prairie. The earliest settlers came from New York and New England. The County-seat, Belvidere, was platted in 1837.
(Taken from The Historical Encyclopedia of Illinois and Harley Haskin's transcription of the 1850 Federal Census of Boone County, Illinois)