75 ILCS 5/2-5
In the event the voters approve of a merger of 2 or more cities, or villages, or incorporated towns or townships, a merger of the affected public libraries shall also occur as follows:
Where the merger affects a city, village, incorporated town or township without a public library and one with a public library, then the existing board of library trustees shall, upon the merger, exercise its powers and duties under this Act, as amended, over the merged territory, and this Act, as amended, shall govern the merged territory.
Where the merger affects 2 or more cities, villages, incorporated towns or townships, each with a public library, then the existing boards of library trustees shall be merged into one new board, and the new board shall thereupon exercise its powers and duties under this Act, as amended, over the merged territory and this Act, as amended, shall govern the merged territory. Such board members shall serve out their respective terms, but as their respective terms expire, successors shall be elected or appointed, as the case may be, only in the case where it is necessary to provide a normal membership for a new board.
In every merger, the board whose territory is being expanded, or the board being merged, shall take such action as is necessary to effectuate the merger approved by the voters, and shall by resolution specify the effective date thereof. In addition, the new library board shall acquire the assets and assume the liabilities of the predecessor library board or boards.
75 ILCS 5/2-5