Geology of the National Parks

History of Saguaro Forest

Hohokam petroglyphs in the Tucson Mountain District west side of Saguaro National Park, Arizona, Creative Commons Attribution-Share Alike 4.0 International / Sunshine-AZ

Javelina Rocks in the Rincon Mountain District east side of Saguaro National Park, Arizona,  Creative Commons Attribution-Share Alike 4.0 International /  Finetooth

Saguaro National Park Pima County, southeastern Arizona. The 92,000-acre...park consists of two separate areas—the Tucson Mountain District about 10 miles...west of the city of Tucson and the Rincon Mountain District about 10 miles...east of the city—that preserve the Sonoran Desert...including the giant saguaro cactus.  The volcanic rocks on the surface of the Tucson Mountain District differ greatly from the surface rocks of the Rincon Mountain District; over the past 30 million years, crustal stretching displaced rocks from beneath the Tucson Mountains of the Tucson Mountain District to form the Rincon Mountains of the Rincon Mountain District...[These mountains] are part of the Basin and Range Province extending from northern Mexico to southern Oregon in the United States.  [The park also has a rock formation], the Pinal Schist, [that] pre-dates the formation of the...Basin and Range about 1.7 billion years.

The earliest known residents of the land in and around what later became Saguaro National Park were the Hohokam, who lived there in villages between 200 and 1450 A.D. Petroglyphs and bits of broken pottery are among Hohokam artifacts found in the park...Subsequent indigenous cultures, the Sobaipuri of the Tucson Basin and the Tohono O'odham to the west, may be descendants of the Hohokam...[Later] residents of and visitors to the lands in and around the park before its creation included...Apaches, Spanish explorers, missionaries, miners, homesteaders, and ranchers.  In 1920 members of the Natural History Society of the University of Arizona expressed interest in establishing a protected area for saguaro, a cactus species familiar to watchers of silent-movie Westerns. In 1928 Homer L. Shantz, a plant scientist and the university's president, joined the efforts to create a saguaro sanctuary.

President Hoover used his power under the Antiquities Act of 1906 to create the monument by proclamation on March 1, 1933.  Congress officially elevated the area known as Saguaro National Monument to the current designation as a National Park in 1994 [during the Clinton administration]. 

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