Great domes of intrusive igneous rock pushed into and deformed surrounding sedimentary layers about 70 million years ago. Erosion later uncovered the domes, revealing the mountains. Mount Ellen's North Summit Ridge (elev 11,522 ft) and Mount Pennell (elev 11,320 ft) top the range.

The arid land and rugged canyons surrounding the Henry Mountains so discouraged early explorers and potential settlers that the range wasn't even named or described until 1869, when members of the Powell rive expedition sighted it. Powell later named the range in honor of one of his supporters, Professor John Henry of the Smithsonian Institution. Tales by Indians of a lost Spanish gold mine have long enticed prospectors, yet only modest amounts of gold were found. Bromide Basin has been the major site for gold and silver mines of the past and present.

Buffalo, brought to the Henrys from Yellowstone National Park in Wyoming in 1941, form one of the few free-roaming herds in the United States. They winter in the southwestern part of the mountains, then move higher as the snow melts.