The Tibet Autonomous Region or Xizang Autonomous Region, often shortened to Tibet or Xizang, is a province-level autonomous region of the People's Republic of China in Southwest China. It was overlayed on the traditional Tibetan regions of Ü-Tsang and Kham. It was formally established in 1965 to replace the Tibet Area, the former administrative division of the People's Republic of China (PRC) established after the annexation of Tibet. The establishment was about five years after the 1959 Tibetan uprising and the dismissal of the Kashag, and about 13 years after the original annexation. The current borders of the Tibet Autonomous Region were generally established in the 18th century and include about half of historic Tibet, or the ethno-cultural Tibet. The Tibet Autonomous Region spans over 1,200,000 km2 (460,000 sq mi) and is the second-largest province-level division of China by area, after Xinjiang. Due to its harsh and rugged terrain, it is sparsely populated at just over 3.6 million people with a population density of 3 inhabitants per square kilometre (7.8/sq mi).