"Signal Hill on Summer Solstice" by Ann Gonzalez.

Human habitation in the Tucson Basin dates back approximately 12,500 years -- to the Pleistocene Age.  The first people were likely descended from those who migrated across a land bridge from Siberia to Alaska;  bands of hunters were roaming the desert grasslands of southern Arizona by about 10,000 BC.

Archeologists have concluded that sites found in the Tucson Basin, along the Santa Cruz River, likely represent the oldest, continuously inhabited area in the United States.

About 2,300 years ago, a group we now call the Hohokam had settled in southern Arizona -- including the Santa Cruz valley.  By AD 700, they had a well-developed agricultural economy including extensive irrigation systems.

Archeological finds in the Rincon Mountain District ofSaguaro National Park show that Hohokam villages existed there for about 600 years -- along Rincon Creek and its tributary washes.  Then, during the 15th century, the Hohokam culture simply vanished.

Contemporary native peoples that would constitute the ethnographic history of the Park include:

• Akimel O'odham (also known as Pima)
• Apache
• Hopi
• Maricopa
• Yaqui
• Tohono O'odham ("Desert People")
• Yavapai
• Zuni

The 2.85-million-acre Tohono O'odham Nation, west of Tucson, is near the Tucson Mountain District of the Park.  The Nation includes the famous Mission San Xavier del Bac, founded in 1700.  The Mission building was completed in 1797, and is a National Historic Landmark.