In 156 BC, Runan was granted to Liu Fei, son of the reigning Emperor Jing as a principality.
A year later, Fei's fief was changed to Jiangdu (江都), and Runan became a commandery.
[1] In late Western Han dynasty, it administered 37 counties, Pingyu (平輿), Yang'an (陽安), Yangcheng (陽城), Liqiang (郦強), Fubo (富波), Nüyang (女陽), Tongyang (鮦陽), Wufang (吳房), Ancheng (安成), Nandun (南頓), Langling (朗陵), Xiyang (細陽), Yichun (宜春), Nüyin (女陰), Xincai (新蔡), Xinxi (新息), Quyang (灈陽), Qisi (期思), Shenyang (慎陽), Shen (慎), Zhaoling (召陵), Yiyang (弋陽), Xiping (西平), Shangcai (上蔡), Qin (浸), Xihua (西華), Changping (長平), Xilu (宜祿), Xiang (項), Xinqi (新郪), Guide (歸德), Xinyang (新陽), Anchang (安昌), Anyang (安陽), Boyang (博陽), Chengyang (成陽) and Dingling (定陵).
[2] In 140 AD during Eastern Han dynasty, the commandery administered 37 counties and had a population of 2,100,788, in 404,448 households.
Later during Sui and Tang dynasties, Runan Commandery became an alternative name of Cai Prefecture.