Zhangjiakou City is a prefecture-level city under the jurisdiction of Hebei Province, also known as "Bird" and "Wucheng", located in the northwest of Hebei Province, China. In the eighth year of Jiajing (A.D. 1529), Zhang zhen, a garrison, opened a small gate on the wall of the North City, which was called the "Small North Gate". Because the city gate is as small as a mouth, it was built in Zhang zhen, so it is called "Zhangjiakou".