The Secretary of the Interior is authorized to acquire such lands and interests in land and to enter into such agreements with the owners of land on behalf of themselves, their heirs and assigns with respect to the use thereof as the Secretary finds necessary to preserve, protect and improve the Antietam Battlefield comprising approximately 1,800 acres in the State of Maryland and the property of the United States thereon, to assure the public a full and unimpeded view thereof, and to provide for the maintenance of the site (other than those portions thereof which are occupied by public buildings and monuments and the Antietam National Cemetery) in, or its restoration to, substantially the condition in which it was at the time of the battle of Antietam. Any acquisition authorized by this section may be made without regard to the limitation set forth in the proviso contained in section 430nn of this title.