SAGUARO Historic Resource Study

Saguaro National Monument consists of two parts. The Rincon Mountain Unit east of Tucson formed the original segment proclaimed by President Herbert Hoover on May 1, 1933, while the Tucson Mountain Unit west of that city was added by proclamation of President John Kennedy on November 15, 1961. Named for the giant cactus of the area, the two units comprise an area of 83,573.88 acres (Rincon Unit—62,835.88 and Tucson Unit—20,738). Most of the acreage was designated as a wilderness area on October 20, 1976.

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Climatically, the two units differ although both are semi-arid. The Rincon Mountain Unit, with a height to approximately 8,600 feet, has a much more developed watershed. Under normal conditions water is more plentiful in that area for winter snow provides spring and early summer moisture, while the monsoons of July and August allow water to flow into September. Historically, this situation attracted settlers to the area for agricultural purposes. At the same time the altitude of the Tucson Mountains, which rise to approximately 4,700 feet, provided an inadequate watershed and thus discouraged settlement until much later. As a result, prospecting and mining played a prominent role there.

The Sonoran Desert vegetation of each monument segment contains differences. In the Rincon Mountain Unit three life zones are apparent. The lower elevation between 2,500 and 4,000 feet contains many varieties of cacti as well as mesquite and palo verde. A transition to semi-desert plants begins around 4,000 feet with scrub oak, yucca, and agave featured. By 7,500 feet the mountains are covered with Arizona yellow pine and ponderosa pine. In contrast the Tucson Mountain Unit contains basically one life zone consisting mainly of cacti, mesquite, palo verde, and ironwood. Some yucca plants are present in the upper parts. Thus, some of the finest areas of Sonoran Desert plant life have been preserved for all the nation to enjoy.