D.C. Code § 10-804

The Secretary of the Interior, with the approval of the National Capital Planning Commission, is hereby authorized, in his discretion, for the best interests of the United States, to sell and convey, in whole or in part, by proper deed or instrument, any real estate held by the United States in the District of Columbia and under the jurisdiction of the National Park Service, which may be no longer needed for public purposes, for cash, or on such deferred-payment plan as the Secretary of the Interior may approve, at a price not less than that paid for it by the government and not less than its present appraised value as determined by him.