50 ILCS 405/1
Except as hereinafter provided in this Act or otherwise specifically provided by law, no county having a population of less than 500,000 and no township, school district or other municipal corporation having a population of less than 300,000 shall become indebted in any manner or for any purpose, to an amount, including existing indebtedness, in the aggregate exceeding 2.875% on the value of the taxable property therein, to be ascertained by the last assessment for State and county taxes, previous to the incurring of such indebtedness or, until January 1, 1983, if greater, the sum that is produced by multiplying such governmental unit's 1978 equalized assessed valuation by the debt limitation percentage in effect on January 1, 1979.
Any county, township, school district and municipal corporation may provide by resolution for the taking of a census of the population thereof in order to determine the number of such population for any and all purposes of this Act. The courts in this State shall take judicial notice of the population of any county or township or school district or municipal corporation as the same may appear from the latest county or township or school district or municipal corporation census so taken. However, no county or township or school district or municipal corporation census shall be taken by the authority of this section, more often than once in 3 years.
50 ILCS 405/1