History of Pima County, Arizona

Pima County, located in southern Arizona, is the second-most populous county in the state and has a rich history that stretches back thousands of years. Named after the Pima Native American tribe, the county was one of Arizona’s original four counties, established in 1864. The area has been a focal point of indigenous culture, Spanish colonization, Mexican rule, and American territorial expansion. Today, Pima County is known for its historical landmarks, cultural diversity, and natural beauty, including its deserts and mountain ranges. Tucson, the county seat, plays a significant role in the region’s economy, education, and tourism.

Pima County Facts

• Founded: November 9, 1864
• Population: Approximately 1.05 million (2023 estimate)
• Area: 9,189 square miles
• Area Codes: 520
• ZIP Codes: 85601–85777
• County Seat: Tucson
• Major Cities: Tucson, Oro Valley, Marana, Sahuarita, Green Valley
• Famous Landmarks: Saguaro National Park, Mission San Xavier del Bac, Pima Air & Space Museum, Arizona-Sonora Desert Museum, Tucson Mountain Park, University of Arizona

---

Early History and Native American Presence (Pre-1600s)

Pima County’s history begins with its earliest inhabitants—Native American cultures that thrived in the desert environment for thousands of years. The region was home to the Hohokam, a farming civilization that developed sophisticated irrigation techniques, and the ancestors of the Tohono O’odham and Pima tribes.

Hohokam Civilization (300 AD–1450 AD)

• The Hohokam were among the earliest settlers in what is now Pima County, establishing an intricate system of irrigation canals, many of which followed the course of modern-day Tucson’s rivers.
• The Hohokam culture is best known for their agricultural success, growing crops such as corn, beans, and squash in the arid desert environment.

Tohono O’odham and Pima Tribes (1500s–Present)

• By the 1500s, the Tohono O’odham and Pima tribes became the dominant Native American groups in the region. They lived off the land through a combination of farming and gathering desert plants.
• The Tohono O’odham, known for their deep connection to the desert, continue to play an essential role in the cultural fabric of southern Arizona today.

Spanish Exploration and Mission Period (1690s–1821)

The arrival of Spanish explorers in the late 17th century marked a significant turning point in the history of Pima County. Spanish missionaries and soldiers established missions and presidios, leaving a lasting cultural and architectural influence on the region.

Father Kino and the Establishment of Missions (1692)

• 1692: Spanish missionary Father Eusebio Francisco Kino arrived in the region, beginning the construction of missions to convert the Native population to Christianity. He founded Mission San Xavier del Bac, located south of Tucson, which became a central hub of Spanish missionary efforts in the region.
• Father Kino’s expeditions helped map much of the Southwest, and his efforts paved the way for Spanish colonization.

Founding of Presidio San Agustín del Tucsón (1775)

• 1775: Spanish settlers, led by Hugo O’Conor, established the Presidio San Agustín del Tucsón, a military fort designed to protect settlers from Apache raids. The presidio marked the official founding of the city of Tucson, which would later become the county seat of Pima County.
• The presidio fostered a small, growing settlement around the fort and mission, laying the foundation for the future development of Tucson.

Mexican Rule and U.S. Acquisition (1821–1854)

After gaining independence from Spain in 1821, Mexico took control of what is now Pima County. During this period, the region saw increased conflict with Native American groups and little development due to its remote location. The Gadsden Purchase in 1854 brought southern Arizona, including Pima County, into the United States.

Mexican Independence and the Santa Cruz Valley (1821–1854)

• Under Mexican rule, the Santa Cruz Valley, which runs through Pima County, remained sparsely populated. The region was a frontier outpost with little Mexican government presence, and it faced continual conflict with the Apache.
• The Mission San Xavier del Bac continued to serve as a cultural and religious center during this period, although it fell into some disrepair due to the lack of resources.

The Gadsden Purchase (1854)

• 1854: The U.S. acquired southern Arizona through the Gadsden Purchase, paying Mexico $10 million for 29,670 square miles of land south of the Gila River. This agreement was designed to facilitate the construction of a southern transcontinental railroad.
• With the Gadsden Purchase, Tucson became part of the U.S. Territory of New Mexico, and American settlers began moving into the area.

Territorial Period and the Formation of Pima County (1854–1912)

The late 19th century marked a period of growth for Pima County as it became part of the Arizona Territory. The establishment of military forts, the development of the railroad, and the discovery of mineral resources transformed Tucson and the surrounding region.

Formation of Pima County (1864)

• 1864: Pima County was officially created on November 9 as one of the original counties of the Arizona Territory. Tucson, which had grown into a small but important settlement, was named the county seat.
• The county was named after the Pima people, who lived in the region and played an essential role in its development.

Apache Wars and the Establishment of Forts (1860s–1880s)

• During the 1860s and 1870s, Pima County was the site of frequent conflict between settlers and the Apache, led by warriors such as Geronimo. To protect settlers, the U.S. military established forts, including Fort Lowell in Tucson.
• The Apache Wars eventually ended in the 1880s, allowing for more peaceful settlement and growth.

The Arrival of the Southern Pacific Railroad (1880)

• 1880: The arrival of the Southern Pacific Railroad in Tucson was a turning point for Pima County. The railroad connected Tucson to major markets and supply lines, spurring economic development and population growth.
• Tucson quickly became a transportation and trade hub for the Arizona Territory, with the railroad facilitating the transport of cattle, minerals, and other goods.

Early 20th Century: Growth and Development (1912–1950s)

Pima County’s growth continued into the 20th century, with Arizona achieving statehood in 1912. The development of infrastructure, agriculture, and education helped solidify Tucson as a major urban center.

Arizona Statehood (1912)

• 1912: Arizona was admitted as the 48th state of the Union, and Tucson became one of the largest cities in the new state. Pima County’s economy was based on agriculture, ranching, and the mining of copper and silver.
• The establishment of the University of Arizona in Tucson in 1885 (prior to statehood) became a central institution for higher education and research, helping to drive the city’s development.

Growth of Agriculture and Military Presence (1920s–1940s)

• During the early 20th century, agricultural development in the Santa Cruz Valley expanded, with crops like cotton and citrus becoming major exports. Irrigation projects along the Santa Cruz River helped sustain these farming efforts.
• World War II brought further growth to Pima County, as Davis-Monthan Air Force Base was established in Tucson in 1940. The base played a critical role during the war and remains an important part of the region’s economy.

Mid-20th Century to Present: Modernization and Population Boom

In the post-war years, Pima County saw rapid urbanization and population growth. Tucson expanded dramatically, becoming a center for education, healthcare, and tourism. The rise of technology industries and research institutions further diversified the county’s economy.

The Post-War Population Boom (1950s–1980s)

• The 1950s and 1960s saw a population explosion in Pima County, driven by an influx of retirees, military personnel, and workers in the defense and technology sectors.
• Tucson became a popular destination for “snowbirds” seeking a warm climate during the winter months, boosting the local economy with tourism and real estate development.

Saguaro National Park and Environmental Conservation (1994)

• 1994: Saguaro National Monument, originally established in 1933 to protect the iconic saguaro cactus, was upgraded to Saguaro National Park. The park, located in eastern and western sections near Tucson, has become one of the county’s most famous attractions, drawing nature lovers and hikers.
• Environmental conservation has become a major focus in Pima County, with the preservation of its desert landscapes and wildlife.

Modern Pima County: Education, Culture, and Technology

• University of Arizona has continued to be a central institution in Pima County, leading research in fields such as astronomy, optics, and environmental science. Tucson is also known for its vibrant arts and cultural scene, with annual events like the Tucson Gem and Mineral Show.
• The county has also become a center for aerospace and defense industries, with companies such as Raytheon establishing operations in the region.

Conclusion

Pima County’s history reflects the broader story of the American Southwest, from its Native American roots through Spanish, Mexican, and American influence. Over the centuries, it has transformed from a remote frontier outpost to a thriving metropolitan area with deep cultural, historical, and environmental significance. With its blend of rich heritage, natural beauty, and modern growth, Pima County continues to be a dynamic and vital part of Arizona’s story.

---

Sources for Pima County History

For further exploration of Pima County’s rich history and culture, visit:

• Arizona Historical Society Museum in Tucson
• Mission San Xavier del Bac
• University of Arizona and its associated museums and research centers
• Saguaro National Park