San Antonio Missions National Historical Park Boundary Expansion Act - Modifies the boundary of the San Antonio Missions National Historical Park to include approximately 151 acres of additional identified land. Bars the use of condemnation authority by the Secretary of the Interior for the acquisition of lands and interests within the boundaries of the park, authorizing acquisition by donation only.
Prohibits this Act, or the park's establishment or management plan, from being construed to create buffer zones outside of the park. Allows the conduct of activities or uses outside the park even if they can be seen or heard from within the park.