70 ILCS 810/21
The board may, for any of the purposes enumerated in this Act, borrow money upon the faith and credit of such district, and may issue bonds therefor. However, a district may not become indebted in any manner or for any purpose to an amount including existing indebtedness in the aggregate exceeding .345% of the assessed value of the taxable property therein, as ascertained by the last equalized assessment for State and county purposes. Except for indebtedness incurred under Section 21.1 of this Act and except for indebtedness incurred to construct, acquire, equip, repair, and renovate buildings or other improvements to land of the district or to acquire equipment for the district, no district may incur indebtedness for any purpose other than the acquisition of land including acquiring lands in fee simple along or enclosing water courses, drainage ways, lakes, ponds, planned impoundments or elsewhere which are required to store flood waters or control other drainage and water conditions necessary for the preservation and management of the water resources of the district, unless the proposition to issue bonds or otherwise incur indebtedness is first certified by the district to the proper election officials, who shall submit the proposition to the legal voters of the district at an election in accordance with the general election law and approved by a majority of those voting upon the proposition. No district may incur indebtedness for the acquisition of land or lands for any purpose in excess of 75,000 acres, including all lands theretofore acquired, unless the proposition to issue bonds or otherwise incur indebtedness is first certified by the district to the proper election officials, who shall submit the proposition to the voters of the district at an election in accordance with the general election law and approved by a majority of those voting upon the proposition. Before or at the time of issuing bonds, the board shall provide by ordinance for the collection of an annual tax sufficient to pay the interest on the bonds as it falls due, and to pay the bonds as they mature. All bonds issued by any forest preserve district must be divided into series, the first of which matures not later than 5 years after the date of issue and the last of which matures not later than 30 years after the date of issue.
70 ILCS 810/21