The Arboretum at Flagstaff is a 200-acre botanical garden on the west side of Flagstaff, Arizona, and one of the highest-elevation public gardens in the United States at 7,150 feet. Its collections center on the high-desert Colorado Plateau, featuring about 750 species with an emphasis on native and drought-tolerant plants, including a notable regional collection of penstemons. The land was once forest and a working ranch, and in 1981 Frances McAllister donated it and created an endowment that established the arboretum in its present form. It also supports research through the Merriam-Powell Research Station and the Southwest Experimental Garden Array, while reflecting the challenges of high-altitude gardening and conservation.