Originally named Hengshan, it is recorded firstly in the Shen nong ben cao jing(Shennong's Classic of Materia Medica). Its name is changed as Changshan in the Song Dynasty and still used today. Changshan is a cosmopolitan species, and the producing area expands from Sichuan, Hubei, Shaanxi and Henan during the Wei and Jin Dynasties to nowadays more than 10 provinces, such as the south of the Yangtze River, Gansu etc. Before the Tang Dynasty, Changshan's original plant is Orixa japonicaThunb., which is changed to Dichroa febrifugaLour. from the Song Dynasty as its main orthodox product.
常山原名恒山，始载于《神农本草经》，至宋代改名常山，自此作为本品正名沿用至今。常山为广布种，其产地由魏晋时期的四川、湖北、陕西、河南等地扩展至今天长江以南及陕西、甘肃等10多个省份。常山的原植物，在唐代以前，以芸香科植物臭常山为正品，至宋代改虎耳草科植物黄常山为主流正品。.
Keywords: Changshan (Radix Dichroae); Chouchangshan (Orixa japonica Thunb.); Huangchangshan (Dichroa febrifuga Lour.).