Shahukou, Youyu, Shanxi 山西右玉杀虎口
Shahukou, on the Shanxi–Inner Mongolia border northwest of Youyu County, is a gap between two hills and was a key opening in the Great Wall to the lands beyond. Called Shahukou (“kill the nomads”) in the Ming and given its present name in the Qing, it was the main gate for migrants “going west of the pass”, and the Qing kept a customs station here.