Any municipality by ordinance may annex any territory contiguous to it even though the annexed territory is dedicated or used for street or highway purposes under the jurisdiction of the Department of Transportation of the State of Illinois, or a county or township highway department if no part of the annexed territory is within any other municipality. After the passage of the ordinance of annexation a copy of the ordinance, with an accurate map of the territory annexed, certified as correct by the clerk of the municipality, shall be filed with the recorder of the county in which the annexed territory is situated and a document of annexation shall be filed with the county clerk and County Election Authority.
65 ILCS 5/7-1-10