Do Walls Work?

History Behind the Great Wall of China and other walls

Historians have a lot to say on whether border walls — a very old idea — are effective. In 2000 BC, Sumeria, part of the Mesopotamian empire in present-day Iraq and Kuwait, built the wall of Mardu. It has crumbled in ruins for centuries. Most famously, beginning in the seventh century BC, the Chinese started to build the Great Wall of China, which event…