Ive come up with some ideas below want to bounce them off of fellow CDers.
I hypothisize that every region in the US has a gateway city. This gateway city is the international city of the region. It is the city that the world looks to when seeing this region. As such, these cities are responsible for the lions share of international commerce and immigration into the region. These cities are (for the most part) also the cultural capitals of their region. Regions are not drawn on state lines, but rather cultural ones. These regions vary greatly in size and can be as small as sliver or as large as many states.
If the mods deem it best, this thread can be moved to the General US forum. I am also not including DC as a capital because its the nations capital.
The regions and their capitals (according to PeterLemonJello anyway):
New England - Capital: Boston
States: Maine, New Hampshire, Vermont, Massachusetts, and Rhode Island
Other cities in the region: Springfield, Manchester, Burlington, Portland
New York - Capital: New York
States: Eastern and Upstate New York, Northern New Jersey, Northeastern Penn. and Conneticut
Other cities in the region: New Jersey Suburbs, Hartford, Ithica, Syracuse, Allentown
Mid-Atlantic - Capital: Philadelphia
States: Eastern Penn. Southern New Jersey, Delaware, and Maryland
Other cities in the region: Baltimore, Trenton, Atlantic City, Wilmington, Harrisburg
Appilachia - Capital: Urban Northern Virginia (DC Area)
States: Virginia, Coastal Virginia, Western Penn, West Virginia, Eastern Kentucky, and Costal Virgina
Other cities in the region: Pittsburgh, Charleston, Richmond, Roanoke
The Southeast - Capital: Atlanta
States: Northeastrn Louisiana, the Carolinas, Northern Florida, Arkansas east of Little Rock, Alabama (minus the coast), Mississippi (minus the coast), Georgia, and Tennessee
Other cities in the region: Charlotte, Raliegh, Knoxville, Birmingham, Nashville, Memphis, Jacksonville, Monroe
Central and Southern Florida - Miami
States: Florida from Tampa and Orlando Southward
Other cities in the region: Tampa, Orlando, Fort Myers, Fort Lauderdale, West Palm Beach
Rust Belt - Capital: Detroit
States: Michigan, Northern Ohio, far Western New York, Northern Indiana
Other Cities in the region: Cleveland, Youngstown, Buffalo, Gary, IN, Akron, Canton
The Midwest - Capital: Chicago
States: Illinois, Indiana (except far Northern), Southern and Western Ohio, Wisconsin, Eastern Iowa, Eastern and Northern Missouri
Other cities in the region: Indianapolis, Milwaukee, Madison, St. Louis, Columbus, Cedar Rapids, Cincinnati
Northern Plains - Capital: Minneapolis
States: Minnesota, far Western Wisconsin, North and South Dakota, Central and Western Iowa, and Nebraska north of Omaha
Other cities in the region: St. Paul, Fargo, Sioux Falls, Omaha, Des Moines
Southern Plains - Capital: Dallas
States: Texas north of San Antonio and East of the Guadalupe Mountains, Arkansas west of Little Rock, Northwestern Louisiana, Oklahoma, Kansas, Western Missouri, and Nebraska south of Omaha
Other cities in the region: San Antonio, Austin, Midland, Lubbock, Oklahoma City, Tulsa, Kansas City, Wichita, Grand Island
Gulf Coast - Capital: Houston
States: Texas along the Gulf Coast and Southeast of Austin, Southern and Central Louisiana, Coastal Alabama, Mississippi, and Gulf Coast Florida (north of Tampa)
Other cities in the region: McAllen, Corups Christi, Baton Rouge, New Orleans, Gulfport, Mobile, Pensacola
Mountain West - Capital: Denver
States: Northern New Mexico, Northeastern Arizona, Utah, Colorado, Northern and Central Nevada, Montana, and Idaho
Other cities in region: Salt Lake City, Albuquerque, Colorado Springs, Billings, Casper, Boise
Southwest - Capital: Phoenix
States: Southern and Central Arizona, Southern New Mexico, Texas west of the Guadalupe Mountains
Other cities in the region: Tucson and El Paso
Southern California - Capital: Los Angeles
States: California South of Fresno, far Southern Nevada
Other cities in the region: San Diego, Las Vegas, Bakersfield, Fresno
Northern California - Capital: San Francisco
States: California north of Fresno, Western Nevada
Other cities in the region: San Jose, Oakland, Reno, Eureka
Pacific Northwest - Capital: Seattle
States: Oregon, Washington
Other cities in the region: Portland, Spokane, Eugene, Redmond
Granted there may be a couple of regions that could be rolled together (for example the Northern Plains with the Midwest or the Southwest with Southern California), but I think this is a good representation.
Ok CD, hack away at it.