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. These are referred to as "Metropolitan Statistical Areas" (MSAs).

As of February 2005, there is now an additional classification, that of a “Metropolitan Division.” The term Metropolitan Division is used to refer to a county or group of counties within a Metropolitan Statistical Area that has a population core of at least 2.5 million. While a Metropolitan Division is a subdivision of a larger Metropolitan Statistical Area, it often functions as a distinct social, economic, and cultural area within the larger region.

The following is a list of the 25 most populated metropolitan statistical areas and Metropolitan Divisions in the United States, according to the 2000 Census:

Rank	Metropolitan Area	Metropolitan Division	States/Territories	Population	Other names*
1	New York--Northern New Jersey--Long Island	&nbsp	NY--NJ--CT	18,323,002	Tri-state Area, New York area, Greater New York
*	&nbsp	Edison, NJ	NJ	2,173,869	&nbsp
*	&nbsp	Nassau-Suffolk, NY	NY	2,753,913	Long Island
*	&nbsp	Newark-Union	NJ	2,098,843	&nbsp
*	&nbsp	New York-Wayne-White Plains	NJ, NY	11,296,377	&nbsp
2	Los Angeles--Long Beach--Santa Ana	&nbsp	CA	12,365,627	The Southland, Southern California (The latter also refers to the entire southern portion of the state)
*	&nbsp	Los Angeles-Long Beach-Glendale	CA	9,519,338	Greater Los Angeles, LA Area
*	&nbsp	Santa Ana-Anaheim-Irvine	CA	2,846,289	Orange County Area, OC
3	Chicago--Naperville--Joliet	&nbsp	IL--IN--WI	9,098,316	Chicagoland, Greater Chicago, Chicagoland and Northwest Indiana (the latter refers to the eastern part extended until South Bend, Indiana)
*	&nbsp	Chicago-Naperville-Joliet	IL	7,628,412	Chicagoland, Greater Chicago
*	&nbsp	Gary	IN	675,971	Chicagoland and Northwest Indiana
*	&nbsp	Lake County-Kenosha County	IL--WI	793,933	&nbsp
4	Philadelphia--Camden--Wilmington		PA--NJ--DE--MD	5,687,147	The Delaware Valley, Tri-state Area
*	&nbsp	Camden	NJ	1,186,999	&nbsp
*	&nbsp	Philadelphia	PA	3,849,647	&nbsp
*	&nbsp	Wilmington	DE--NJ--MD	650,501	&nbsp
5	Dallas--Fort Worth--Arlington	&nbsp	TX	5,161,634	The Metroplex, DFW
*	&nbsp	Dallas-Plano-Irving	TX	3,451,226	&nbsp
*	&nbsp	Fort Worth-Arlington	TX	1,710,318	&nbsp
6	Miami--Fort Lauderdale--Miami Beach	&nbsp	FL	5,007,564	South Florida metropolitan area
*	&nbsp	Fort Lauderdale-Pompano Beach-Deerfield Beach	FL	1,623,018	&nbsp
*	&nbsp	Miami-Miami Beach-Kendall	FL	2,253,362	Metro Dade
*	&nbsp	West Palm Beach-Boca Raton-Boynton Beach	FL	1,131,184	&nbsp
7	Washington--Arlington--Alexandria	&nbsp	DC--VA--MD--WV	4,796,183	Baltimore-Washington Metropolitan Area (now defunct)
*	&nbsp	Bethesda-Frederick-Gaithersburg	MD	1,068,618	&nbsp
*	&nbsp	Washington-Arlington-Alexandria	DC--VA--MD--WV	3,727,565	&nbsp
8	Houston--Baytown--Sugar Land	&nbsp	TX	4,715,407	Houston Metropolitan Area
9	Detroit--Warren--Livonia	&nbsp	MI	4,452,557	Metro Detroit, Southeast Michigan, Southeastern Lower Michigan**
*	&nbsp	Detroit-Livonia-Dearborn	MI	2,061,162	Metro Detroit
*	&nbsp	Warren-Farmington Hills-Troy	MI	2,391,395	&nbsp
10	Boston--Cambridge--Quincy	&nbsp	MA--NH	4,391,344	Greater Boston
*	&nbsp	Boston-Quincy	MA	1,812,937	&nbsp
*	&nbsp	Cambridge-Newton-Framingham	MA	1,465,396	&nbsp
*	&nbsp	Essex County	MA	723,419	&nbsp
*	&nbsp	Rockingham County-Strafford County	NH	389,592	&nbsp
11	Atlanta--Sandy Springs--Marietta	&nbsp	GA	4,247,981	Atlanta Metropolitan Area
12	San Francisco--Oakland--Fremont	&nbsp	CA	4,123,740	The Bay Area***
*	&nbsp	Oakland-Fremont-Hayward	CA	2,392,557	East Bay
*	&nbsp	San Francisco-San Mateo-Redwood City	CA	| 1,731,183	The City (San Francisco only), The Peninsula (San Mateo County only), Marin (Marin County Only)
13	Riverside--San Bernardino--Ontario	&nbsp	CA	3,254,821	Inland Empire
14	Phoenix--Mesa--Scottsdale	&nbsp	AZ	3,251,876	The Valley of the Sun
15	Seattle--Tacoma--Bellevue	&nbsp	WA	3,043,878	Greater Puget Sound
*	&nbsp	Seattle-Bellevue-Everett	WA	2,343,058	&nbsp
*	&nbsp	Tacoma	WA	700,820	&nbsp
16	Minneapolis--St. Paul--Bloomington	&nbsp	MN--WI	2,968,806	The Twin Cities****
17	San Diego--Carlsbad--San Marcos	&nbsp	CA	2,813,833
18	St. Louis	&nbsp	MO--IL	2,698,687	Greater St. Louis
19	San Juan--Caguas--Guaynabo	&nbsp	PR	2,579,248
20	Baltimore--Towson	&nbsp	MD	2,552,994
21	Pittsburgh	&nbsp	PA	2,431,087
22	Tampa--St. Petersburg--Clearwater	&nbsp	FL	2,395,997	Tampa Bay Area
23	Denver--Aurora	&nbsp	CO	2,196,028
24	Cleveland--Elyria--Mentor	&nbsp	OH	2,148,143	Greater Cleveland, Northeast Ohio
25	Kansas City--Overland Park	&nbsp	KS--MO	1,836,038

* Not necessarily equivalent to the Census definition of the metropolitan area.
** This metropolitan area of Detroit does not include certain outlying areas considered to be in Southeast Michigan, such as Genesee and Livingston Counties, nor does it include Canadian cities. A larger metropolitan area containing the Windsor, Ontario area is used internationally.
*** The Bay Area is a much larger area than the OMB's rather limited MSA, corresponding more closely to the San Jose - San Francisco - Oakland Combined Statistical Area
**** The main cities of the Twin Cities are generally considered to be Minneapolis and St. Paul; Bloomington is generally considered to be a suburb of the two even though it is in a three-way tie for the third largest city in Minnesota.

For a complete list, see List of United States metropolitan statistical areas by population.

See also

• Core Based Statistical Area
• Demographics of the United States
• List of metropolitan areas by population
• List of regions of the United States
• United States micropolitan area
• List of the largest urban areas of the European Union by population
• Largest metropolitan areas in the Americas

External links

• U.S. Census 2000 Metropolitan Area Rankings; ranked by population
• U.S. Census 2000 Metropolitan Area Rankings
• [definitions of all Metropolitan Statistical Areas, Metropolitan Divisions]
• U.S. Census Metropolitan Area Estimates (1990s)
• U.S. Census Metropolitan and Micropolitan Statistical Area Definitions