Wall are first built in the states during Warring States Period to protect themselves from disturbing of other countries. Chu States is said to the first one to built this and successfully made Qi State's troop retreat. After Qin united the whole nation, he ordered to connected all the seperate wall into the Great Wall.

what up i thought that a alien built the wall because who in the right mind builds a wall that big

to keep some kind of invadors out i forget their names

Common People, Criminals, and soldiers built the Great Wall Of China to protect it from invaders.

The great wall was build to keep out invaders and it was build in 221 B.C.