The Secretary may identify other significant sites of the colonial and Revolutionary periods of American history in the city of Boston, Massachusetts, and its environs, which are related to the historical park created by this subchapter, and, with the consent of the owner or owners thereof, may mark them appropriately and make reference to them in any interpretive literature.
16 U.S. Code § 410z–1 - Acquisition of additional sites
(a) StudiesIn addition to the properties described in section 410z of this title, the Secretary shall study the properties described in this section to determine the feasibility and suitability of including them within the Boston National Historical Park. In making such studies, he may enter into tentative agreements with any owners thereof for their inclusion in said park and he may enter into options, for a nominal consideration, for the purchase of such properties, but no additional properties may be added to the park except by an act of the Congress. Studies shall be made of the following properties:
(b) Cooperative agreements authorized
In furtherance of the general purposes of this subchapter as prescribed in section 410z of this title, the Secretary is authorized to enter into cooperative agreements with the city of Boston, the Commonwealth of Massachusetts, or any private organization to mark, interpret, restore, and/or provide technical assistance for the preservation and interpretation of any properties listed in section 410z of this title, or portions thereof, which, in his opinion, would best be preserved in private, municipal, or State ownership, in connection with the Boston National Historical Park. Such agreements shall contain, but shall not be limited to, provisions that the Secretary, through the National Park Service, shall have right of access at all reasonable times to all public portions of the property covered by such agreement for the purpose of conducting visitors through such properties and interpreting them to the public, that no changes or alterations shall be made in such properties except by mutual agreement between the Secretary and the other parties to such agreements, except that no limitation or control of any kind over the use of any such properties customarily used for church purposes shall be imposed by any agreement. The agreements may contain specific provisions which outline in detail the extent of the participation by the Secretary in the restoration, preservation, and maintenance of such historic properties.
(c) Identification and marking of significant historical sites