The Secretary of the Interior is authorized, in his discretion, to acquire in behalf of the United States, through donations or by purchase at prices deemed by him reasonable or by condemnation in accordance with section 3113 of title 40, lands, buildings, structures, and other property, or interests therein, which he may determine to be of historical interest in connection with the Antietam Battlefield site, the title to such property or interests to be satisfactory to the Secretary of the Interior: Provided, That payment for such property or interests shall be made solely from donated funds. All such property and interests shall be a part of the Antietam Battlefield site and shall be subject to all laws and regulations applicable thereto.