55 ILCS 5/1-4006
All the county officers of the petitioning county shall continue to hold their respective offices until their respective terms of office shall expire, and shall perform the duties of their respective offices arising in the territory which, before the Governor's proclamation aforesaid, had constituted the petitioning county, and shall receive the fees and compensation thereof, in the manner hereinafter provided. They shall keep their offices at the county seat of the adjoining county, in the court house of said county, in such rooms as may be selected by the county board of the adjoining county; and within ten days after the date of the proclamation as aforesaid, by the Governor, they shall remove all the files and records, books, papers, and furniture of their respective offices to the court house of the adjoining county, which shall thereafter be held and taken to be the files, records, books, papers and furniture of the adjoining county as it shall be constituted after the date of the proclamation aforesaid.
55 ILCS 5/1-4006