Unfortunately, the national park established in 1919 did not protect all of the Grand Canyon: Marble Canyon, geologically a part of Grand Canyon, and the western portion of the Grand Canyon, were not included. During the 1960's, plans to build two huge dams in the Grand Canyon prompted a national protest. Bridge Canyon Dam in the western Grand Canyon would have flooded part of the park, Marble Canyon Dam would have eliminated the whitewater river run, and the wild heart of the canyon would have been lost. Finally, in 1973, Congress passed a law expanding the park to include all of Marble Canyon and the Grand Canyon except the southwestern portion on the Hualapai and Havasupai Indian reservations. The new law also addressed a long-standing injustice done to the Havasupai Tribe by expanding their reservation to include traditional lands upstream of Supai Village and on the South Rim.

For more details on the administrative history of Grand Canyon National Park, see Polishing the Jewel: An Administrative History of Grand Canyon National Park