The most significant change in the Grand Canyon National Park Enlargement Act of 1975 was the enlargement of the Havasupai Reservation to include lands, particularly on the plateaus above Havasu/Cataract Canyon, that should have been included when the reservation was recommended by the governing army in the 1880's (See my entries in Sep 2009.) Approximately 185,000 acres were repatriated to Havasupai sovereignty from the Kaibab National Forest and Grand Canyon National Park and Monument. Here is the official map, with the Reservation diagonally striped (the labels refer to the pre-1975 areas, and see the 1967 map at the end of this entry.
The map was made more exact by wording in the Act itself that the map
"shall delineate a boundary line generally one-fourth of a mile from the rim of the outer gorge of the Grand Canyon of the Colorado River"
"shall traverse Havasu Creek from a point on the rim at Yumtheska Point (west side) to Beaver Falls to a point on the rim at Ukwalla Point" (east side). (My parentheses.)
For more clarity, here is the current BLM map covering Havasupai lands. I have circled in black the three places named in the traverse of Havasu Creek.
The easternmost part of the Reservation boundary does not follow the ¼-mile rule, but rather runs along the boundary that existed before 1975 between the Park and the Forest i.e., ½ mile from the center line of the 1925 road survey. This three-section wide slab of Forest (east of the two vertical black lines) was subject in 1975 to an existing grazing allotment, called the Raintank. After a last-ditch effort, grazing privileges on the Raintank were extended by the legislation for not more than 10 years; however, the allottee yielded his privileges very soon after the Act passed. The map shows this jump from the old Park-Forest boundary to the ¼-mile setback section.
The western side of the Reservation, one township wide (plus a bit), was the southern extension of the second GCNMonument. The BLM map has the Park come down to the south section line of 13, T32N R6W (pink circle), while the official map has it heading west a bit north of that section line, probably because of the private land in that section.
Adjoining the Reservation on the north (except north of what was the Raintank), a 95,300-acre swath of the Park (from the ¼-mile setback to the river) was designated as Havasupai Use Lands, the uses being "grazing and other traditional purposes". This designation (cross-hatching on the map) is not a restriction or reservation on the Park (as Wilderness designation would be), but a privilege for the Havasupai.
Since neither Park nor Havasupai will fence their common boundary, it makes sense that uses on both sides of this "line" will be in accord. This seems to have been the case over the past 35 years; indicating that a controversy that caused acrimonious and needless anguish over almost a century seems to have come to an end. We should be grateful, for both the ¼-mile setback and the three named locations are imprecise enough to generate endless bickering were the parties so minded (as proven by the case for the next boundary segment, that between Park and Hualapai Reservation).
Here is the Automobile Club of Southern California's "Indian Country" map for 1967. Only the northern piece of the Havasupai Reservation is shown.