65 ILCS 5/8-5-1
Except as hereinafter provided in this Division 5, no municipality having a population of less than 500,000 shall become indebted in any manner or for any purpose, to an amount, including existing indebtedness in the aggregate exceeding 8.625% on the value of the taxable property therein, to be ascertained by the last assessment for state and county purposes, previous to the incurring of the indebtedness or, until January 1, 1983, if greater, the sum that is produced by multiplying the municipality's 1978 equalized assessed valuation by the debt limitation percentage in effect on January 1, 1979.
The indebtedness limitation set forth in this Section may be inapplicable to indebtedness incurred for the purpose of pumping water from Lake Michigan to one or more municipalities having a population of less than 500,000, whether before or after such indebtedness is incurred, if the majority of voters in such municipality approve such inapplicability at an election on the issue held in accordance with the general election law. The governing authority of any such municipality may, by proper ordinance or resolution, cause the proposition of the inapplicability of the limitation of indebtedness set forth in this Section to the indebtedness incurred for such purpose to be certified to the proper election authorities and submitted to the voters of the municipality at a regularly scheduled election in accordance with the general election law. If a majority of the votes cast on the proposition are in favor thereof, indebtedness incurred for the purpose of pumping water from Lake Michigan to one or more municipalities shall not be subject to the limitation set forth in this Section.
The indebtedness limitation set forth in this Section shall not apply to any indebtedness of any municipality incurred to finance the cost of the acquisition, construction or improvement of water or wastewater treatment facilities mandated by an enforceable compliance schedule developed in connection with the federal Clean Water Act or a compliance order issued by the United States Environmental Protection Agency or the Illinois Pollution Control Board.
Any village or incorporated town may provide by resolution, and any city may provide by ordinance, for the taking of a census of the population thereof in order to determine the number of that population for any purpose of this Division 5. The courts in this state shall take judicial notice of the population of any municipality as it appears from the latest municipal census so taken. However, no municipal census shall be taken by the authority of this section, oftener than once in 3 years.
The amendatory Act of 1973 is not a limit upon any municipality which is a home rule unit.
65 ILCS 5/8-5-1