when was the great wall of china was built

As early as the Warring States Periods (476 BC - 221 BC), the ruling powers began to build walls as a defense against the northern nomadic tribes. Later, during the state of Chu was the first to build a wall, Qi, Yan, Wei, Zhao and Qin, they all built some sections of wall. Then the subsequent dynasties also built that and the most well-known ones were made in the Han and Ming dynasties. The current well-preserved sections was made in the Ming Dynasty.

It was begun to be built during the Qin Dynasty. Hope this helps!