The Arboretum at Flagstaff is a 200-acre (81-hectare) arboretum that houses 2,500 species of drought-tolerant plants native to the high-desert Colorado Plateau, home to 6,000 plant species, 34 of which are listed as endangered, the Zion National Park and the Grand Canyon. It was founded in 1981 as a private non-profit organization with ?The Transition Zone Horticultural Institute? as its official name.

The Arboretum was originally a forested area and a working ranch, and the home of Frances McAllister in the late 1960s. In 1981, McAllister started her long-sought dream of building an arboretum when she donated the property and made its financial endowment. It is also home to the Merriam-Powell Research Station and has been visited by more than 23,000 people in 2009. Located 3.8 miles (6.1 kilometers) south of the United States Route 66 on Woody Mountain Road in Arizona, the Arboretum is a nature center, research station and botanical garden situated 7,150 above sea level.

Several miles of trails wind down through one of the biggest collections of high-country shrubs, native plants, and trees in the nation. Everyday, a live Birds of Prey show is offered. It also has a gift shop and picnic areas. While research was the original and primary focus, over the years Arboretum at Flagstaff has become known as a haven for out-of-town and local visitors who want to learn more about the native plants and animals found in northern Arizona.

The Research Department collaborates with other departments to attain The Arboretum?s mission which is to focus in plant biology, invasive weeds, plant conservation, and horticultural trials, among other studies.

The Arboretum is a charter member of the Center for Plant Conservation and currently has 30 national collection plant species under its care. The Arboretum at Flagstaff seeks to conserve these species using ex-situ (off-site) propagation, seed storage, and monitoring methods.