Saved 1/7/2023
Text of S. 1296 (93rd): Grand Canyon National Park Enlargement … as of Jan 3, 1975 (Passed Congress version). S. 1296 (93rd): Grand Canyon National Park Enlargement Act
This 1975 act combined a number of federal lands - like Marble Canyon - into the Grand Canyon and also expanded the Havasupai reservation. Of note for planning and access is "nonmembsrs of the tribe shall be permitted to have access across such lands at locations established by the Secretary in consultation with the Tribal Council in order to visit adjacent parklands" - which as of the 2015 Backcountry Management Plan and as far as I know into 2023 had not been established.