Qinghai (Chinese: 青海; pronounced [tɕʰíŋxài]), formerly known in English as Kokonur, is a province of the People's Republic of China located in the northwest of the country. As one of the largest province-level administrative divisions of China by area, the province is ranked fourth-largest in size, but has the third-smallest population. Located mostly on the Tibetan Plateau, the province has long been a melting pot for a number of ethnic groups including the Han, Tibetans, Hui, Tu, Mongols, and Salars. Qinghai borders Gansu on the northeast, Xinjiang on the northwest, Sichuan on the southeast, and the Tibet Autonomous Region on the southwest. Qinghai province was established in 1928 under the Republic of China period during which it was ruled by Chinese Muslim warlords known as the Ma clique. The Chinese name, "Qinghai" is named after Qinghai Lake (cyan sea lake), the largest lake in China. The province was known formerly as Kokonur in English, derived from the Oirat name for Qinghai Lake.