D.C. Code § 10-129

When in accordance with law or mutual legal agreement, spaces or portions of public land are transferred from the jurisdiction of the Director of the National Park Service, as established by §§ 6-404, 10-104, 10-106, 10-123, 10-129 and 10-137, to that of the Mayor of the District of Columbia, or vice versa, the letters exchanged between them of transfer and acceptance shall be sufficient authority for the necessary change in the official maps and for record when necessary.