55 ILCS 5/6-5007
The resolution authorizing the issuance of such bonds shall specify the total amount of bonds to be issued, the form and denomination of the bonds, the date they are to bear, the place where they are payable, the date or dates of maturity, which shall not be more than 20 years after the date the bonds bear, the rate of interest which shall not exceed 4% per annum and the dates on which interest is payable.
Such resolution shall prescribe all the details of the bonds and shall provide for the levy and collection of a direct annual tax upon all taxable property within the county sufficient to pay the principal thereof at maturity and to pay the interest thereon as it falls due, which tax shall not be subject to any statutory limitations relative to taxes which may be extended for county purposes.
55 ILCS 5/6-5007