70 ILCS 1870/17
The bonds or certificates shall be sold by the corporate authorities of the Port District in such manner as the Board determines, except that if issued to bear interest at the maximum rate permitted in "An Act to authorize public corporations to issue bonds, other evidences of indebtedness and tax anticipation warrants subject to interest rate limitations set forth therein", approved May 26, 1970, as now or hereafter amended, the bonds shall be sold for not less than par and accrued interest, and except that the selling price of the bonds bearing interest at a rate less than the maximum rate permitted in that Act shall be such that the interest cost to the district of the money received from the bond sale shall not exceed such maximum rate annually computed to absolute maturity of such bonds or certificates according to standard tables of bond values.
70 ILCS 1870/17