All bonds issued under authority of this Act shall be payable over a period of not less than five nor more than twenty years from the date of issue and shall bear interest at a rate not to exceed six per cent per annum, payable semiannually. The proceeds of the bonds shall be used only for the purpose of constructing or completing playgrounds or athletic fields, and grandstands or seating facilities therefor, as Living War Memorials.
70 ILCS 1275/9