The Dong, a Kam-Sui people of southern China, are one of the 56 ethnic groups officially recognized by the People's Republic of China. They are famed for their native-bred Kam Sweet Rice, carpentry skills, and unique architecture, in particular a form of covered bridge known as the 'wind and rain bridge'. The Dong people live mostly in eastern Guizhou, western Hunan, and northern Guangxi provinces. Small pockets of Dong speakers are also found in Tuyen Quang province, northern Vietnam. Nanning was originally founded during the Yuan Dynasty (1271 - 1368), although there was a county seat here called Jinxing as far back as 318 CE. Opened to foreign trade by the Chinese in 1907, Nanning grew rapidly. From 1912 to 1936 it was the provincial capital of Guangxi, replacing Guilin. Due to its proximity to the Vietnamese border Nanning became a major centre for supplying Ho Chi Minh's North Vietnam during the Second Indochina War (Vietnam War).