Why was the Great Wall of China built by Shi Huang Ti?

Seriously, you can't say that the wall wasy built by him. The wall was originally built during the warring states period. After Emperor Shihuangdi unified China, he ordered around 300000 soldiers and civilians to build the wall. In later dynasties, the emperors also ordered to extend and reenforce the wall. The wall we see today were almost built during the Ming Dynasty.