It was an important chokepoint, protecting Xi'an and the surrounding Guanzhong region from the North China Plain.

The fortress was the seat of Tongguan County, but was demolished in the 1950s to make way for the Sanmenxia Dam and reservoir.

Chinese civilization first grew up along the Wei, Luo, and Yellow River valleys of the Loess Plateau before expanding out into the "barbarians regions.

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.

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).