How many people built the great wall of china and how long did it take?

Many people built the great wall of china about 1 million people worked on the great wall of china. most people that built the great wall of china were forced to do it and many of them lost their lives building the great wall of china. Some of it was built over 2000 years ago, several parts were added or re-built over several centuries. I think the most recent rebuilding was about 500 years ago.