The main path of the Great Wall of China extends over 5,500 miles from Hushan to Jiayuguan—tackling this massive monument on foot is a difficult task! It would take between 15 and 18 months to walk the Ming section of the Great Wall of China from end to finish. The job could be done more quickly if you were a Chinese worker who followed the wall in order to make money. In fact, the labor force used to build the Great Wall was large enough that some estimates say that up to 20 percent of the population may have been involved at any given time. The wall was built during the 14th century under the reign of Emperor Yongle (1360-1425). At its greatest extent, the wall crossed 1,500 miles of land with an overall height of more than 13 feet. It was made of stone and covered with plaster. There are two types of walls: the main part made of stone and the lesser part made of wood. The wall was designed not only to protect against invaders but also as a form of social control by preventing people from fleeing the country without permission. It took about 10 years to build the first 100 miles of the wall and another five years to complete it all the way to its terminus in Beijing. However, building it went beyond just one person or group of people; instead, it was an organized government project that employed many workers from across China.