Monterey County was one of the original counties of California, created in 1850 at the time of statehood. Parts of the county were given to San Benito County in 1874.

The county derived its name from Monterey Bay. The word itself is composed of the Spanish words monte and rey, which literally means "Hill" and "King". The bay was named by Sebastian Vizcaino in 1602, in honor of Gaspar de Zuniga y Acevedo, Conde de Monterrey, the Viceroy of New Spain.