70 ILCS 805/23
Each forest preserve district shall have the power to transfer the interest earned from any moneys of the district into the respective fund of the district that is most in need of the interest income, as determined by the board of commissioners. This Section does not apply to any interest earned that has been earmarked or restricted by the board for a designated purpose. This Section does not apply to any interest earned on any funds for purposes of the Illinois Municipal Retirement Fund under the Pension Code or tort immunity under the Local Governmental and Governmental Employees Tort Immunity Act. Interest earned on these exempted funds shall be used only for the purposes authorized for the respective exempted funds from which the interest earnings were derived.
70 ILCS 805/23