Both the Wulan Pass and Wulan County were located on the intersection of the north route of the Silk Road and the Yellow River, an important geographic position. They were first established in Emperor Wu’s reign during the Northern Zhou dynasty, and Wulan County was once abolished in the Sui dynasty and then reestablished in the early Tang. In the reign of Empress Wu Zetian, the seat of the city was moved and continued to exist in tandem with the Wulan pass until the end of the Tang dynasty. Some scholars think that the Wulan and Huining Passes, respectively belonging to Wulan and Huining Counties, were established on the east and west banks of the river, whereas other scholars think that the Wulan Pass and the seat of Wulan County were both located within ancient Beichentan City at today’s Beicheng village in Shuanglong township, Jingyuan County, Gansu province, and that they were all on the east bank of the Yellow River together with the Huining Pass and Huining County. By investigating the epitaphs and assorted relics from Wulan of the Sui and Tang dynasties unearthed from the ancient city site of Beichengtan and records of Dunhuang manuscripts about the position of the Huining Pass and the relationship between Chemu Valley and Wulan Bridge, this paper considers that the Wulan Pass and Wulan County were in fact located in ancient Beichengtan city, and in the second year of the Tianshou era in Wu Zetian’s reign( 691), the Wulan County seat was moved 7 li northward to the Pingchuan area due to the gradual scouring of the river. The epitaphs record that the Fan family moved from Dunhuang to Wulan County in Huizhou Prefecture, settled there and were finally buried in Beichengtan, indicating the importance of the Hexi Corridor and Gaolan Road, both parts of the north route of the Silk Road
