Laozi Went out of Hangu Pass

Hangu Pass was heavily defended by the State of Qin, as the only reasonable route to invade the Qin. Laozi was stopped by frontier guards when leaving Hangu Pass for the west. Then Laozi wrote the"Dao De Jing" at Hangu Pass.   Lao Tzu is the "moral" Holy Ghost Valley is the birthplace of Taoism.