The area of Pima County is 9,186 square miles.
Historically the size of Pima County was much larger. Pima County extended south of the Gila River, and covered most of Arizona that was acquired from Mexico by the Gadsen Purchase.
Pima County was one of the original counties designated by the First Territorial Leglislative Assembly. It was the fourth county created by this assembly.
Later the counties of Maricopa, Pinal, Cochise, Graham and Santa Cruz were taken from Pima County.
Arizona blue book [Phoenix, Ariz.] : R. Mofford, Secretary of State, 1986. Page 164.
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