55 ILCS 5/1-4001
Whenever any number of legal voters, not less than two hundred, one-half of such number being owners or life tenants of real estate, residing in any county in this State, shall petition the county board of their own county, for leave to have their own county united and annexed to any adjoining county, and shall also petition the county board of the adjoining county, to which they desire their county to be united and annexed, for leave to have their own county united and annexed to such adjoining county, it shall be the duty of the several county boards so petitioned, to order that the propositions provided for in this Division shall be submitted to the legal voters of their respective counties. The several county boards shall certify the propositions to the proper election officials who shall submit the question at a general election in accordance with the general election law. In addition to the requirements of the general election law, the notices of said election shall include the name of each of the two counties, and shall state that the proposition to be voted upon will be whether the county of (naming the county whose legal voters have petitioned for union and annexation) shall be united and annexed to the county of (naming the adjoining county to which the legal voters have petitioned to be united and annexed): Provided, that such proposition shall not be submitted or voted upon more often than once in 5 years.
55 ILCS 5/1-4001