Illinois Counties records can vary greatly from county to county in both level of quality and quantity. You will find four forms of court records that are most likely to have details relevant for your genealogical research. For Definitions of all court terms see the Genealogy Encyclopedia.
The circuit court clerk’s office holds administrations, probate documents, and wills. The recorder of deeds holds leases, deeds, and mortgages. Researchers submitting requests in writing should use the county officer title and the heading “County Courthouse,” along with the address.
Researchers should note that many Illinois counties were divided into other counties. Therefore, some counties may have deed records available from their parent counties. Although, most deed records begin with the date that the present county was founded. The records from the earliest courts should be consulted for information on counties from the territorial period. Those records are: St. Clair: Court of the District of Cahokia; Randolph: French Provincial Council; Madison, Gallatin, and Johnson: court of common pleas; Edwards, White, Jackson, Pope, Monroe, Crawford, and Bond: county court; Franklin, Union and Washington: justices’ court. The early records from the counties of Franklin, Cook, and Jackson no longer exist. Fires destroyed them.
See also a list of links to county and county seat government run websites.