Western Zhou Dynasty
The construction of the Great Wall of China began in China's Western Zhou Dynasty (771 BC). The purpose of the construction was to protect against the nomadic tribes of Northern China, also known as the Yanyun. Later, during the Period of the Warring States from 476 BC to 221 BC, the Seven States of Qi, Chu, Han, Zhao, Wei, and Qin engaged in the construction process and continued building the Great Wall for self defense.
Qin and Ming Dynasties
After Qin Shihuang, the first emperor of China, united the seven warring states, he ordered his slaves to connect the scattered walls of the seven states. This construction of the Great Wall continued from the Qin Dynasty in 221 BC through the Ming Dynasty in 1644. During the Ming Dynasty, the wall was strengthened and heightened. This was the peak of the Great Wall's Construction.
The Great Wall of China was built as a complete defense system. Some of the features include passes, tunnels, and watchtowers and beacons. The central command of the Ming Dynasty, for example, was able to relay vital information down the length of the wall through the million soldiers standing guard. Officials of lesser rank were stationed at the ends of the wall, while higher-ranking officials were stationed within the 11 Great Wall garrisons to support frontier defenses.
The Great Wall during Ming Dynasty was 33 feet tall. In flat areas, the wall was built taller than other regions and also has added defense lines for extra protection. In the mountainous regions, the wall was built in a more cost effective manner. The wall is lower with the steep terrain helping its defensive advantage. The Great Wall stretches for 5,500 miles from Eastern Shanhaiguan to Lop Nur in the Western Frontier.
Some of the more notable areas of the Great Wall include the "North Pass," "West Pass," "Pass" of Shanhaiguan, the steep watchtowers of JinShanling, the South East tower of Jinshanglin, and the "silver" wall of Liaotianling. Each area has its own particular qualities that give the wall a quality separate from the other regions. For example, the wall of Liaotianling appears silver in color due to the high quantity of metals in the area's mines. Some sections have been renovated for use by tourists, while other parts of the wall remain too dangerous to hike.