Here's what I've come up with in terms of different size levels of various frum communities in North America (covering the gamut from Modern Orthodox to Chasidic):
300,000 or more: Greater New York (including northern and central New Jersey as well as Fairfield County, Connecticut)
15,000-20,000 or even more: Los Angeles, South Florida (Miami to West Palm Beach), Chicago, Toronto, Montreal, Baltimore
5,000-12,000: Philadelphia (including southern New Jersey), Cleveland, Detroit, Boston
1,500-5,000: Washington DC (including Silver Spring), Pittsburgh, Atlanta, Denver, San Diego, Las Vegas, Phoenix, St. Louis, Seattle, Dallas, Houston, San Francisco Bay area
750-1,500: Columbus, Cincinnati, Rochester, Buffalo, Hartford, Providence, Memphis, Kansas City, Milwaukee, Indianapolis, Minneapolis/St. Paul, Portland (Oregon), Vancouver, Ottawa, Winnipeg
Am I accurate, or does this hierarchy need to be adjusted in some way?