65 ILCS 5/7-1-16
Where a municipality adjoins another municipality in one or more portions of its boundaries, it may be annexed thereto as follows, notwithstanding that territory not a part of either of the municipalities may lie between or be surrounded by the municipalities:
A petition shall be presented to the circuit court for the county, wherein the annexing municipality is situated, asking that the question of annexation be submitted to the electors of both municipalities. The petition shall be signed by not less than 10% of the total number of electors of the municipality sought to be annexed who voted at the last preceding general municipal election or 250 such electors, whichever figure is the smaller. Furthermore, if a majority of those voting, in a municipality sought to be annexed, upon the question of annexation vote against the annexation of that municipality when the question is first submitted, any petition thereafter presented to the court for the annexation of the same municipality shall be signed by not less than 1/8 of the electors of that municipality who voted at the last preceding general municipal election.
The court thereupon shall order the question of annexation submitted to the electors of both municipalities at an election to be held in each municipality. The clerk of the circuit court shall certify the question to the proper election authorities at an election in accordance with the general election law for submission. No election on the question of annexation shall be held within 22 months after the same question has been voted upon.
65 ILCS 5/7-1-16