70 ILCS 1525/3
Money received from the proceeds of taxes levied for payment of principal of and interest upon such bonds shall be deposited in a special fund of such park district suitably designated for identification and such fund shall be faithfully applied to the payment of bonds and interest thereon for which such taxes were levied.
If such money is not immediately necessary for the payment of said bonds or if such bonds cannot be purchased before maturity then said money may be invested under the direction of the commissioners in direct obligations of the United States of America, which shall mature or which shall be subject to redemption by the holder thereof at the option of such holder prior to the date such funds shall be required for the purpose for which they are held. Interest accruing on and profit or loss realized from the investment of such funds shall be credited or charged to such special account.
70 ILCS 1525/3