Megalopolis is the name for large region around Washington DC that includes Beltway freeway corridor?

BosWash is the name for the large region around Washington DC that includes the Beltway freeway corridor.

The region extends from Boston in the north to Washington, DC, in the south, and includes the cities of Baltimore, Philadelphia, and New York City. BosWash is home to over 50 million people and is one of the most densely populated areas in the United States. The region is a major center of economic activity, with a GDP of over $4 trillion. BosWash is also home to many cultural and educational institutions, including the Smithsonian Institution, the Library of Congress, and Harvard University.