Was there one Great Wall of China? Explain

The Great Wall of China, built more than 2,000 years ago, stands as one of the monumental feats of ancient engineering. But before the Great Wall, warring Chinese dynasties built many other walls for protection. There are 7,000 watchtowers, blockhouses for soldiers, and beacons to send smoke signals. Nineteen walls have been built that were called the Great Wall of China. The first was built in the 7th century BC.

Yes.

Explanation:

The Great Wall of China was to protect China from northern invaders like the MONGOLS.

a big wall across the mexican border so no drugs, terrorist, or illegal immigrants can come through : )