McDowell Sonoran Preserve is a vast protected desert area in Scottsdale, Arizona, spanning about 30,500 acres in a continuous stretch of Sonoran Desert habitat. Often described as the largest city park in the United States, it is managed as a nature reserve created through land purchases funded by a sales tax increment approved by Scottsdale voters, reflecting a community commitment to permanent protection. Supported in part by the McDowell Sonoran Conservancy, it serves both conservation and recreation, offering more than 180 miles of trails for hiking, mountain biking, rock climbing, running, and horseback riding, with free access from sunrise to sunset.