(a) Additional lands, waters, and interests therein
In order to add to the Grand Canyon National Park certain prime portions of the canyon area possessing unique natural, scientific, and scenic values, the Grand Canyon National Park shall comprise, subject to any valid existing rights under the Navajo Boundary Act of 1934, all those lands, waters, and interests therein, constituting approximately one million two hundred thousand acres, located within the boundaries as depicted on the drawing entitled "Boundary Map, Grand Canyon National Park," numbered 113–20, 021 B and dated December 1974, a copy of which shall be on file and available for public inspection in the offices of the National Park Service, Department of the Interior.

(b) Abolition of Grand Canyon and Marble Canyon National Monuments
For purposes of sections 228a to 228j of this title, the Grand Canyon National Monument and the Marble Canyon National Monument are abolished.

(c) Study and report to Congress of suitability of lands included within enlarged boundaries; submission date
The Secretary of the Interior shall study the lands within the former boundaries of the Grand Canyon National Monument commonly known as the Tuckup Point, Slide Mountain, and Jensen Tank areas to determine whether any portion of these lands might be unsuitable for park purposes and whether in his judgment the public interest might be better served if they were deleted from the Grand Canyon National Park. The Secretary shall report his findings and recommendations to the Congress no later than one year from January 3, 1975.