A megalopolis, or megapolis, is a very large, heavily populated urban complex that consists of several large cities and suburbs that adjoin each other. An example of a megalopolis is BosWash, the metropolitan area in northeast U.S. that stretches from Boston to Washington D.C.
The BosWash megalopolis has a population of approximately 44 million people, or roughly 16% of the U.S population. Another U.S. megalopolis is the Great Lakes megalopolis, which is the largest mega-region in North America with approximately 55 million people. The Great Lakes region is actually an international megalopolis as it encompasses several Canadian cities such as Toronto and Ottawa.