Main Cities of US Mega-Regions

Name the main cities found in each US mega-region which are defined in Wikipedia as "clustered networks of US-American cities, the population of which currently ranges or is projected to range from about 57 to 63 million by the year 2025". The list of mega-regions and main cities in each is based on the site america2050.org (note that some cities that may not actually be in certain geographical regions, such as Southern California, could still be included in that mega-region)