75 ILCS 5/1-1

For the purposes of this Act the term "corporate authorities" means, as applied to cities, villages and incorporated towns, the corporate authorities as defined in Section 1-1-2 of the Illinois Municipal Code, and, as applied to townships, the Township Board of Trustees. The terms "board", "board of trustees" or "board of library trustees" means any Board of Library Trustees of a city, village, incorporated town or township.