Amdo encompasses a large area from the Machu (Yellow River) to the Drichu (Yangtze River). Historically, culturally, and ethnically a Tibetan area, Amdo was administered by a series of local rulers from around the mid-18th century. From the mid 18th century until the mid 20th century, much of Amdo was ruled by local kings and chiefs or by warlords. Much of Amdo was incorporated into the newly formed Qinghai Province, and today Amdo has 8 prefectures: Golog, Malho, Tsolho, Tsobyang, and Tsoshar in Qinghai Province, Ganlho in Gansu Province, and Ngawa in Sichuan Province.