Changzhi City, Shanxi Province, is located in the southeast of Shanxi Province, the southwest of Shangdang Basin, between 35°53 '~36°15' north latitude, 112°27 '~113°00' east longitude. The total area of the county is 1029 square kilometers. Eldest son County is a warm temperate continental monsoon climate, affected by the alternating cold and warm air forces, four distinct seasons, mild climate, rain and heat in the same season, strong monsoon. As of 2018, Eldest Son County has jurisdiction over 7 towns and 5 townships, with the county government based in Danzhu Town. According to the seventh census data, as of midnight on November 1, 2020, the permanent population of Eldest Son County was 298,690.

Eldest son County has a long history, because of the ancient period of King Yao's eldest son Dan Zhu, was sealed in this county name. During the sixteen States of the Eastern Jin Dynasty, Murong Yong proclaimed himself emperor according to his eldest son and became the capital of Western Yan. Sui KaiHuang years called the eldest son county, since then, the county name has not been changed. In ancient times, it was a thoroughfare of Jinzhou-Henan and Qinjin-Jin. The county seat is only 20 kilometers away from the urban area, and provincial roads 228, 326 and Changlin Expressway pass through the county. Taijiao Railway and Zhongnan Railway converge here, which is the largest railway marshalling station along the Zhongnan Railway. In the south of the eldest county, there is the sheep head mountain, the first emperor Yan tasted all kinds of grass here, Jiahe, teaching people farming. In the west lies Miyuki Mountain, the birthplace of the famous myth "Jingwei Reclamation". Xianweng Mountain in southwest China, there are 250 million years of fossil wood community. And the Warring States Tomb, Faxing Temple, Chongqing Temple and other historical sites, a total of 12 national key cultural relic protection units.
In December 2019, it became a pilot unit for the construction of the country's rural governance system.