16 U.S.C. § 283a

(a) Authority of Secretary; manner and place; concurrence of State owner Within the boundaries of the Guadalupe Mountains National Park, the Secretary of the Interior may acquire land or interests therein by donation, purchase with donated or appropriated funds, exchange, or in such other manner as he deems to be in the public interest. Any property, or interest therein, owned by the State of Texas, or any political subdivision thereof, may be acquired only with the concurrence of such owner. (b) Adjacent or vicinal land; exchange of property; cash equalization payments In order to facilitate the acquisition of privately owned lands in the park by exchange and avoid the payment of severance costs, the Secretary of the Interior may acquire approximately 4,667 acres of land or interests in land which lie adjacent to or in the vicinity of the park. Land so acquired outside the park boundary may be exchanged by the Secretary on an equal-value basis, subject to such terms, conditions, and reservations as he may deem necessary, for privately owned land located within the park. The Secretary may accept cash from or pay cash to the grantor in such exchange in order to equalize the values of the properties exchanged. In order to provide for an adequate entrance road into the McKittrick Canyon area of the park, the Secretary may accept title to and interests in lands comprising a right-of-way for a road or roads outside of the boundary of the park from United States Highway numbered 62 and 180 to the park boundary, and in exchange therefor he may convey title to and interests in lands comprising a right-of-way from said highway to the boundary which have been donated to the United States. The Secretary may accept cash from or pay cash to the grantor in such exchange in order to equalize the values of the properties exchanged. Lands and interests in lands comprising the right-of-way acquired pursuant to this subsection shall be administered as part of the park.