Previously known as Yazhou-fu, the city is first mentioned during the Zhou Dynasty (1122-255 BC). It served as a county seat during the Qin and Han Dynasties, but was subsequently taken by nomadic tribes. After being reintegrated into the Chinese Empire in the late 5th century, it was made the seat of the Ya Prefecture in 604. The modern Ya'an county was established in 1912. It became the provincial capital of Xikang province in 1951, but has been a municipality under the administration of Sichuan province since 1955, when Xikang province was merged and became a part of Sichuan province. The first giant panda was found in Baoxing County of Ya'an; Ya'an is also the origin of Artificial planting tea of the world; Mengding Mountain in Mingshan County, has been keeping seven tea trees, which are believed to be the origins of tea, for more than 1,000 years. Yaan is truly a rain city. There is rain 180 days of a year.