Migrates of Beidijun County Town in Eastern Han Dynasty

Beidijun was an important county of frontier from Qin Dynasty to Western Han Dynasty.Beidijun was invaded by Qiang and Hun in the last years of Western Han Dynasty,since then the area under its jurisdiction was decreased,and the county town was migrated.Beidijun was reset in Eastern Han Dynasty.Although the county town used the old name of Beidijun,but it was not the actual location of the Western Han Dynasty,and changes several times as the Qiang riot.The county town of Beidijun had been migrated to Guanzhong before 141 A.D.