16 U.S.C. § 430h-2
In order to further the consolidation of land comprising Vicksburg National Military Park, the Secretary of the Interior is authorized, upon such terms and conditions as he may deem necessary, to transfer to the city of Vicksburg, Mississippi, for school purposes, a tract of park land containing three and one-tenth acres, more or less, now under revocable permit to said city, acting through its board of education, and to transfer to the Mississippi State Highway Commission a tract of park land containing one and thirty-two hundredths acres, more or less, now under revocable permit to said commission for use as a site for a weighing station: Provided, That, from among the land designated as tracts 199, 201, 202, 203, 204, 205, 206, and 216 on map Numbered NMP-VIC-7007, said city and highway commission shall transfer in exchange to the United States, for addition to Vicksburg National Military Park, such land or interests therein as may be mutually agreed upon and which are approximately equal in value to the properties being acquired in each case.
16 U.S.C. § 430h-2