The county is named after the Pima Native Americans, also known as Tohono O'odham, who are indigenous to this area.

The original county consisted of all of Arizona Territory east of longitude 113° 20' and south of the Gila River.

The SDCP addresses natural and cultural resources, ranches, endangered species compliance and wildlife corridors.

The United States Office of Management and Budget has designated Pima County as the Tucson, AZ Metropolitan Statistical Area.

[18][19] Pima County is governed by a five-member Board of Supervisors who set ordinances and run services for the areas that do not fall within any city or town's jurisdiction.

The county Board of Supervisors acts under powers delegated by state law, mainly related to minor ordinances and revenue collection.

The Pima County Board of Supervisors is responsible for steering public policy in the region.

The five-member board provides direction to the County Administrator, Jan Lesher,[20] and the county's various departments as they work to ensure safe communities, nurture economic development, sustainably manage natural resources and protect public health.

In addition to overseeing the delivery of a host of municipal services, from roads to parks and libraries and law enforcement, board members also are responsible for approving the county budget.

Elected to four-year terms, board members also set the amount of taxes to be levied.

[21] Along with the Board of Supervisors the Arizona State Constitution allows for 7 other county elected officials.

[29] Incorporated towns within the county with municipal police departments are Tucson, Marana, Oro Valley, and Sahuarita.

After voting Democratic through 1930s and 1940s, it swung Republican following major population increase after World War II, becoming a Republican-leaning county.

In both 2016 and 2020, Donald Trump became the first Republican since Bob Dole in 1996 to fail to win 40% of the county's vote.