The commandery was established by the Qin state in 248 BC, after Qin general Meng Ao attacked Taiyuan, then part of the State of Zhao, and annexed 37 Zhao cities including Yuci (榆次), Xincheng (新城) and Langmeng (狼孟).
[1] The seat was Jinyang (晉陽, near modern Taiyuan city), a former capital of Zhao.
In 2 AD, the commandery administered 21 counties, namely Jinyang, Junren (葰人), Jiexiu (界休), Yuci (榆次), Zhongdu (中都), Yuli (于離), Cishi (茲氏), Langmeng (狼孟), Wu (鄔), Yu (盂), Pingtao (平陶), Fenyang (汾陽), Jingling (京陵), Yangqu (陽曲), Daling (大陵), Yuanping (原平), Qi (祁), Shang'ai (上艾), Lüchi (慮虒), Yangyi (陽邑), and Guangwu (廣武).
[2] By 140 AD, the number of counties had decreased to 16, and the population to 200,124, or 30,902 households.
[3] In 280 AD, after the unification of Western Jin, the commandery had 13 counties (Jinyang, Yangqu, Yuci, Yuli, Yu, Langmeng, Yangyi, Daling, Qi, Pingtao, Jingling, Zhongdu, Wu) and 14,000 households.