Most of Lake Powell is in an American state.
Arizona ( [ ɛərᵻˈzoʊnə , _ ærᵻ - ] ) ( Hoozdo Hahoodzo [ xòːztò xɑ̀xòːtsò ] O'odham : Alĭ ṣonak [ ˡaɺi ˡʃonak ] ) is a state in the southwestern region of the United States . Lake Powell is a reservoir on the Colorado River , straddling the border between Utah and Arizona ( most of it , along with Rainbow Bridge , is in Utah ) . Utah ( [ ˈjuːtɔː ] or [ ˈjuːtɑː ] ) is a state in the western United States .