But by 3,500 BCE, Sumer is going to be able to check off all five boxes. Now Sumer itself, we'll go through those five boxes in a second, I promise kids. The Sumer itself is about the size of Massachusetts. It was located on the eastern edge of what we call Mesopotamia. Medicine day Iraq, the Persian Gulf area, right where the Tigris and Euphrates come together to pour into that Persian Gulf. But they were able to do five things that nobody else could do that gives them the title of their earliest civilization. Now number one, you need to have advanced cities.