Fairfax County, Virginia

Fairfax County is a county in Virginia, United States, about 15 miles west of Washington, D.C. across the Potomac River. It had a population of 1,150,309 at the 2020 census, an estimated 1,167,873 by 2025, and covers 391 square miles (1,013 km2) centred near 38°50′N 77°17′W — making it the most populous county in Virginia and one of the most populous in the country.

Fairfax is the county seat, though it is a legally separate independent city, not a part of the county it serves; the county courthouse and jail sit inside a small county-owned exclave carved out of the city, and that complex’s postal code is 22030. The county holds 3 incorporated towns and dozens of unincorporated communities grouped into 9 magisterial districts — Braddock, Dranesville, Franconia, Hunter Mill, Lee, Mason, Mount Vernon, Providence, Springfield and Sully — and it runs on Eastern time. Its FIPS code is 51059.

Towns & Villages in Fairfax County

Virginia’s independent-city system means Fairfax County has no incorporated cities of its own — the City of Fairfax and the City of Falls Church sit entirely inside the county’s boundary lines but are legally separate jurisdictions, each with its own government, schools and mayor. What the county does have are 3 incorporated towns and dozens of census-designated places (CDPs), the unincorporated communities the Census Bureau names for statistical purposes but which have no town government of their own. The table below covers the 3 towns; a second table lists the county’s 25 largest CDPs by population, out of several dozen recognized in total.

Clifton, incorporated in 1902, is one of the smallest towns in Virginia and sits at the opposite end of the scale from Herndon and Vienna, both of which run their own police departments and sit on Metro’s Silver and Orange lines respectively.

Tysons is the renamed successor to “Tysons Corner” — the Census Bureau made the change official in 2016 after county officials and the Tysons Partnership dropped “Corner” from local branding ahead of the Silver Line’s 2014 opening. Its ZIP codes are still shared with neighbouring McLean and Vienna, since Tysons has never had a standalone post office. Springfield’s CDP boundary above covers only the historic core; the ZIP-code-defined “Greater Springfield” area used by USPS and local businesses runs across four ZIPs (22150–22153) and totals well over 100,000 residents.

ZIP Codes

• 20170 — Herndon
• 22180–22183, 22185 — Vienna
• 20124 — Clifton
• 20120–20122 — Centreville
• 20190, 20191, 20194 — Reston
• 22101–22103, 22106 — McLean (also serves the CIA headquarters area at Langley)
• 22003 — Annandale
• 22015 — Burke
• 22124 — Oakton
• 22102, 22182 — Tysons (shared with McLean and Vienna)
• 20151–20153 — Chantilly
• 22150–22153 — Greater Springfield
• 22066 — Great Falls
• 22030–22033 — City of Fairfax and the county government complex

Smaller CDPs such as Fair Oaks, Bailey’s Crossroads, Brambleton, Franklin Farm and Franconia do not carry a distinct postal ZIP of their own; mail there is delivered under a bordering town or CDP’s code, which is why the table above leaves those cells blank rather than guessing.

Geography

Fairfax County straddles the Fall Line, where the rolling Piedmont uplands in the county’s northwest give way to the flatter Atlantic Coastal Plain along the Route 1 corridor in the southeast. The Potomac River forms the county’s entire eastern and northern boundary, and the Occoquan River and Occoquan Reservoir — a drinking-water supply for much of Northern Virginia — mark the southern line with Prince William County. Smaller lakes, including Burke Lake, Lake Accotink and Lake Fairfax, sit inside county parkland.

The county borders Loudoun County to the northwest, Prince William County to the southwest, and Arlington County to the northeast, and it wraps entirely around the independent cities of Fairfax and Falls Church. The independent city of Alexandria adjoins its southeastern edge. Across the Potomac lie Montgomery County and Prince George’s County, both in Maryland.

Demographics

The county’s population was 1,150,309 at the 2020 census, up from roughly 1.08 million in 2010, and the 2025 estimate puts it near 1,167,873. Centreville and Reston are the two largest communities, each with more than 60,000 residents. Median household income runs about $145,164, well above Virginia’s statewide median household income of roughly $87,249 (ACS 5-year estimate), reflecting the concentration of federal, defense and technology jobs. Population density works out to about 2,942 people per square mile of land area.

Economy & Local Life

Federal government employment anchors the county’s economy: roughly 28,000 federal workers live and work in the county, alongside the CIA’s headquarters in the Langley section of McLean and the Office of the Director of National Intelligence, also in McLean. Fairfax County Public Schools employs about 26,829 people, making it the second-largest employer, and Inova Health System, headquartered in Falls Church with its flagship hospital in the county, employs roughly 26,000. Tysons has grown into what local planners call the largest suburban business district in the country, with more than 26 million square feet of office space and corporate headquarters for Capital One, Freddie Mac, Booz Allen Hamilton and MITRE. George Mason University’s main campus, the largest public research university in Virginia, sits just outside the City of Fairfax line. The county’s signature annual event is Celebrate Fairfax!, a three-day festival held each June at the Fairfax County Government Center.

History

Fairfax County was formed on June 19, 1742, out of Prince William County, and named for Thomas Fairfax, 6th Lord Fairfax of Cameron, proprietor of the Northern Neck land grant that once covered much of Northern Virginia. Its early economy ran on tobacco plantations worked by enslaved people; by the 1860 census, enslaved residents made up close to a fifth of the county’s population, concentrated on estates including George Washington’s Mount Vernon in the county’s southeast. The Battle of Chantilly, also called Ox Hill, was fought in the county on September 1, 1862, and killed two Union generals, Philip Kearny and Isaac Stevens, during the retreat after Second Manassas. The county stayed largely rural until the mid-20th century, when Cold War-era federal and defense hiring across the Potomac in Washington and Arlington drove one of the fastest suburban growth spurts in the country, transforming crossroads communities like Tysons into office and commercial hubs by the 1980s.

Getting There

Interstate 495, the Capital Beltway, loops through the county’s eastern half, joined by Interstate 66 running east-west and Interstate 95 and Interstate 395 in the south and east. The Dulles Toll Road and Dulles Access Road (Virginia 267) connect Tysons to Washington Dulles International Airport, whose main terminal sits on county land that stretches into neighbouring Loudoun County.

• Washington, D.C. — about 15 miles northeast of Tysons
• Alexandria — about 10 miles southeast of the county’s southern edge
• Arlington — immediately northeast, across the county line
• Manassas — about 15 miles southwest, in Prince William County

Washington Dulles International Airport is the county’s primary commercial airport; Ronald Reagan Washington National Airport, in Arlington, is closer for travellers in the county’s eastern communities. The nearest Amtrak station is in the City of Alexandria; Virginia Railway Express commuter trains stop within the county at Burke Centre, Rolling Road, Backlick Road and Franconia-Springfield.

Frequently Asked Questions

Where is Fairfax County?
It sits in Northern Virginia along the Potomac River, directly across from Washington, D.C. and Montgomery County, Maryland.

What is the population of Fairfax County?
1,150,309 at the 2020 census, with an estimated 1,167,873 by 2025, making it Virginia’s most populous county.

How big is Fairfax County?
391 square miles (1,013 km2) of land, plus about 15 square miles of water along the Potomac and Occoquan.

What is the county seat of Fairfax County?
Fairfax is the county seat, even though it is a legally separate independent city and not part of the county itself. The courthouse complex sits inside a small county-owned exclave within the city.

How many towns are in Fairfax County?
Three incorporated towns — Herndon, Vienna and Clifton — plus dozens of unincorporated CDPs such as Reston, Centreville, McLean, Annandale, Burke and Tysons.

Are the City of Fairfax and Falls Church part of Fairfax County?
No. Both are independent cities under Virginia law, with their own governments, even though the county surrounds them and shares services and statistics with them.

What ZIP codes cover Fairfax County?
More than two dozen, including 20170 (Herndon), 22180–22185 (Vienna), 22101–22106 (McLean), 20120–20122 (Centreville) and 20190–20194 (Reston).

More counties in this state: Towns and villages in Virginia. See also Arlington County and Loudoun County.