Depending on how broadly the researcher wants to define the geographic boundaries of the Washington DC metropolitan area for his/her study, there are several options listed below. Note that the geographic codes used below (CSA, CBSA, and county) can be found in the NCCS Counties file (nccs.counties table on the data web).
By Census CSA (Combined Statistical Area):
CSA: 548
CSA Name: Washington-Baltimore-Northern Virginia, DC-MD-VA-WV Combined Statistical Area
Population (Census 2006 est.): 8,129,395
By Census CBSA (Core Based Statistical Area):
CBSA: 47900
CBSA Name: Washington-Arlington-Alexandria, DC-VA-MD-WV Metropolitan Statistical Area
Population (Census 2006 est.): 5,226,411
By Jurisdiction *
Jurisdiction Name: DC-NoVA-Suburban MD
Included County Codes:
District of Columbia
11001 DISTRICT OF COLUMBIA
Suburban Maryland
24027 HOWARD COUNTY
24031 MONTGOMERY COUNTY
24033 PRINCE GEORGES COUNTY
24003 ANNE ARUNDEL COUNTY
Northern Virginia
51510 ALEXANDRIA CITY
51013 ARLINGTON
51059 FAIRFAX COUNTY
51600 FAIRFAX CITY
51610 FALLS CHURCH CITY
51107 LOUDOUN COUNTY
51683 MANASSAS CITY
51153 PRINCE WILLIAM COUNTY
51685 MANASSAS PARK CITY
Population (Census 2006 est.): 4,658,743
Population (Census 2006 est.) by Jurisdiction Components:
| Jurisdiction | Population |
| District of Columbia | 585,459 |
| Northern Virginia | 2,042,792 |
| Suburban Maryland | 2,030,492 |
Note: This is not Census defined. The "jurisdiction" definition was used by reporter Drew Lindsay of the Washingtonian.