Tongguan County is a county in Shaanxi, China, administered as part of the prefecture-level city of Weinan. Its eponymous county seat, formerly romanized as Tungkwan,[a] lies south of the confluence of the Wei and Yellow Rivers. It is the southeastern corner of the Ordos Loop, the point at which the Qin Mountains turn the Yellow River sharply eastward, forcing it into the North China Plain. During the Middle Ages, the Tong Pass or Tongguan pass was an important chokepoint, protecting Xi'an and the surrounding Guanzhong area from outside attack. It now lies at the intersection of Shaanxi, Shanxi, and Henan.
|• Total||526 km2 (203 sq mi)|
|• Density||290/km2 (740/sq mi)|
|Time zone||China Standard (UTC+8)|
|Literal meaning||High Pass|
Chinese civilization first grew up along the Wei, Luo, and Yellow River valleys of the Loess Plateau before expanding out into the "barbarians" who held the North China Plain. The state of Qin fortified the Hangu Pass to the east of Tongguan as its eastern border and it continued to protect the Chinese heartland from outside attack during the Qin and Han dynasties. During the Eastern Han that succeeded Wang Mang's short-lived "Xin dynasty", the guards at Hangu reversed themselves and protected Luoyang in the plains from attacks coming from the west. From the time of the AD 211 Battle of Tongguan, however, Tongguan replaced the Hangu Pass as the principal strategic post between the Guanzhong area and the North China Plain. Under the Tang, the fall of Tongguan to An Lushan's rebels led directly to their capture of the capital Chang'an (now Xi'an, Shaanxi).