The Granite Mountains of Arizona is a mountain range in the Sonoran Desert of southern Arizona. It is located in extreme western Pima County, Arizona, bordering southeast Yuma County. The Granite Mountains are an 18-mile (29 km) long range, trending mostly northwest-southeast; the north end of the range turns more northerly and aligns with the Aguila Mountains of Yuma County 6 miles north. The Granite Mountain's highest point is unnamed at 2490 ft. The west and south end of the mountains lie at the southeastern beginning of the San Cristobal Valley flowing northwest and north to the Gila River Valley. The east side of the range borders the north-flowing Growler Valley. The southern end of the mountains are adjacent to a water divide where south-flowing drainages enter into portions of northern Sonora, Mexico.