Boyce Thompson Arboretum, founded in 1924 by mining engineer William Boyce Thompson, became Arizona’s oldest and largest botanical garden and one of the oldest botanical institutions west of the Mississippi. Created as both a public garden and a research center for useful plants from arid regions, it grew into a major conservation and education site along Queen Creek beneath Picketpost Mountain. Its grounds combine formal collections with natural desert and riparian habitat, supporting more than 2,600 arid-land plant species and rich wildlife, including 270 recorded bird species. Despite early financial hardship and drought, it endured, later becoming a state park while preserving its nonprofit and scientific roles.