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Cactus Forest Drive, Saguaro National Monument [PDF ebook] 
(Illustrated Edition)

Saguaro National Park is an American national park in Pima County, southeastern Arizona. The 92, 000-acre (37, 000 ha) park consists of two separate areas—the Tucson Mountain District (TMD) about 10 miles (16 km) west of the city of Tucson and the Rincon Mountain District (RMD) about 10 miles (16 km) east of the city—that preserve Sonoran Desert landscapes, fauna, and flora, 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. Uplifted, domed, and eroded, the Rincon Mountains are significantly higher and wetter than the Tucson Mountains. The Rincons, as one of the Madrean Sky Islands between the southern Rocky Mountains and the Sierra Madre Oriental in Mexico, support high biodiversity and are home to many plants and animals that do not live in the Tucson Mountain District.
Earlier residents of and visitors to the lands in and around the park before its creation included the Hohokam, Sobaipuri, Tohono O'odham, Apaches, Spanish explorers, missionaries, miners, homesteaders, and ranchers. In 1933, President Herbert Hoover, using the power of the Antiquities Act, established the original park, Saguaro National Monument, in the Rincon Mountains. In 1961, President John F. Kennedy added the Tucson Mountain District to the monument and renamed the original tract the Rincon Mountain District. Congress combined the Tucson Mountain District and the Rincon Mountain District to form the national park in 1994.
The park gets its name from the saguaro (Carnegiea gigantea), a large cactus that is native to the Sonoran Desert and that does not grow naturally elsewhere. Rincón—as in Rincon Mountains, Rincon Creek, and Rincon Valley—is Spanish for corner, and refers to the shape of the mountain range and its footprint. The name Tucson derives from Papago-Piman words cuk ?on [?t?uk??n], meaning dark spring or brown spring. Tank or Tanque refers to a small artificial pool behind a dam that traps runoff in an existing natural depression. Madrean derives from Madre in Sierra Madre (Mother Mountains).