Cities, for the first time in history, are now home to more than 50 percent of the world’s population. This is an incredible demographic shift, and in their rise to prominence, urban centers have begun to shape national and global-level discussions. After all, there are now megacities in Asia and Latin America with larger populations than some European countries. These megacities drive more than 70 percent of the world’s economic activity, and some of their local governments are acting across national borders to strike their own trade deals and address climate change issues.