Province (pop., 2002 est.: 25,930,000), north-central China. It is bordered by Mongolia, the autonomous regions of Xinjiang, Inner Mongolia, and Ningxia, and the provinces of Shaanxi, Sichuan, and Qinghai. It has an area of 141,500 sq mi (366,500 sq km). Its capital is Lanzhou. For centuries a passage between the upper Huang He (Yellow River) region and western China, it became part of Chinese territory in the 3rd century BC. It was renowned as the entranceway into China used by Marco Polo. Eastern Gansu is the main site of earthquakes in China; in 1920 an earthquake there destroyed many towns and caused 246,000 deaths. Wheat is the province's chief crop, and wheat flour rather than rice is the basis of the local diet.