Pinal County, Arizona: History
Pinal County was carved out of neighboring Maricopa County and Pima County on February 1, 1875, during the Eighth Legislature. In the August 18, 1899, issue of The Arizona Magazine, the name "Pinal" is said to come from the pine-clad Pinal Mountains. Pinal County was the second-fastest-growing county in the U.S. between 2000 and 2010.
In 2010, CNN Money named Pinal County as the second fastest growing county in the USA.