During the period any such cooperative agreement remains in force, one-half of the gross proceeds from all lands covered by the agreement and to which the United States holds title shall be paid by the State to the United States. All such payments shall be credited to the purchase price the State is to pay the United States for the land, such purchase price to be an amount equal to the total sum expended by the United States in acquiring the lands. Upon payment of the full purchase price, the Department of Natural Resources is authorized to take a conveyance of such lands in the name of the State of Illinois.
20 ILCS 820/3