In the United States, the Office of Management and Budget (OMB) has produced a formal definition of metropolitan areas, which are organized around county boundaries (except in New England, where cities and towns are more significant than counties as geographical and political units.) These are referred to as "Metropolitan Statistical Areas" (MAs). If an MA is large enough and can be subdivided into meaningful sub-metropolitan areas, then the MA is considered a "Consolidated Metropolitan Statistical Area" (CMSA), with each subdivision called a "Primary Metropolitan Statistical Area" (PMSA). The largest MAs in the United States are all CMSAs.
The following is a list of the top metropolitan areas in the United States, according to the 2000 census:
| Metropolitan Area | States | Type | Population | Local nickname |
|---|---|---|---|---|
|
New York--Northern New Jersey--Long Island | NY--NJ--CT--PA | CMSA | 21,199,865 | |
| CA | CMSA | 16,373,645 | The Southland | |
| IL--IN--WI | CMSA | 9,157,540 | Chicagoland | |
| DC--MD--VA--WV | CMSA | 7,608,070 | ||
| CA | CMSA | 7,039,362 | The Bay Area | |
| PA--NJ--DE--MD | CMSA | 6,188,463 | ||
| Boston--Worcester--Lawrence | MA--NH--ME--CT | CMSA | 5,819,100 | |
| Detroit--Ann Arbor--Flint | MI | CMSA | 5,456,428 | Metro Detroit |
| Dallas--Fort Worth | TX | CMSA | 5,221,801 | The Metroplex |
| Houston--Galveston--Brazoria | TX | CMSA | 4,669,571 | |
| Atlanta | GA | MSA | 4,112,198 | |
| Miami--Ft. Lauderdale | FL | CMSA | 3,876,380 | |
| Seattle--Tacoma--Bremerton | WA | CMSA | 3,554,760 | |
| Phoenix--Mesa | AZ | MSA | 3,251,876 | |
| Minneapolis--St. Paul | MN | MSA | 2,968,806 | The Twin Cities |