Minuteman Missile National Historic Site Boundary Modification Act - Amends the Minuteman Missile National Historic Site Establishment Act of 1999 to modify the boundary of the Minuteman Missile National Historic Site in South Dakota by including in the Historic Site a visitor facility and administrative site located on a specified parcel of land that consists of approximately 25 acres of land in the Buffalo Gap National Grassland.
Transfers administrative jurisdiction over such land from the Secretary of Agriculture to the Secretary of the Interior.
Modifies the boundary of the Buffalo Gap National Grassland to exclude the transferred land.