While some aspects about the history of incision of the canyon are debated by geologists, several recent studies support the hypothesis that the Colorado River established its course through the area about 5 to 6 million years ago.
Mõned aspektid kanjoni ajaloos on geoloogide seas vaidluse all, kuid mitmed hiljutised uuringud toetavad seisukohta, et Colorado jõgi rajas oma voolusängi sellesse piirkonda 5-6 miljonit aastat tagasi.