Data Center Alley: how Ashburn became the world’s data center capital

How it started

JLARC traces the cluster to the establishment of an internet exchange point in the 1990s, which attracted major telecommunications and early internet companies to Northern Virginia[3]. Loudoun County dates its own story to 1992, when engineers from Metropolitan Fiber Systems and UUNet connected local fiber networks in a parking garage in Vienna, Virginia, creating the first commercial internet exchange point[1]. America Online opened its global headquarters in Ashburn in 1996, and UUNet followed in 1998[1].

Zoning did the rest. Loudoun says its Zoning Administrator determined data centers were permitted “by right” — without additional legislative approval — in many office parks[1], which let the cluster grow building by building without a public hearing for each one.

How big it is now

JLARC says 80 percent of Virginia’s data center industry is concentrated in three Northern Virginia localities: Loudoun, Prince William and Fairfax[3], and that Loudoun alone is about half of the state’s industry by sites, square footage and estimated energy use[3]. The county counts approximately 233 existing buildings totaling about 56.5 million square feet, built or under various stages of construction[1]; its economic development arm cites 53.3 million square feet in operation or under development[4].

The often-repeated claim that most of the world’s internet traffic passes through Ashburn should be read carefully. Loudoun County Economic Development says much of the world’s internet traffic passes through its digital infrastructure[4], and Washingtonian reported in September 2016, without naming a source, an estimate of 70 percent of the world’s web traffic[5]. That figure is a decade old and its origin is not documented.

What it pays for

Loudoun County says data centers generated $1.2 billion in real and personal property tax revenue in FY2026, 39% of the county’s overall budget, and projects $1.3 billion, or 40%, in FY2027[1]. JLARC put data center revenue at 31 percent of total local tax revenue in Loudoun and 7 percent in Prince William in FY2023[3]. The county says the revenue has let it lower the real property tax rate for homeowners nearly every year for a decade[6], while warning that growth in this revenue will plateau within five to 10 years[6].

The grid problem

Loudoun says data centers in the county cumulatively use at least 3 gigawatts of power at any given time, according to PJM[2], and that the regional grid has become strained in large part due to increased electrical demand from data centers over the past 20-plus years[2]. Route Fifty reported in July 2022 that accelerating growth was producing transmission constraints in a pocket of eastern Loudoun that primarily serves large customers[7].

New lines are a state matter, not a county one: Loudoun notes the State Corporation Commission, not the county, reviews and approves high-voltage transmission routing, and the county may only file a notice of participation in SCC cases[8]. Virginia Mercury reported in April 2026 that the SCC approved above-ground construction of the Golden-Mars high-voltage line in Loudoun[9]. JLARC’s commissioned forecast found unconstrained demand for power in Virginia would double within 10 years, and that building enough infrastructure for unconstrained data center demand will be very difficult[10].

The rules changed

In March 2025 Loudoun Now reported the Board of Supervisors voted 7-2 to eliminate by-right data centers, and narrowly adopted a resolution grandfathering applications submitted by Feb. 12 for projects more than 500 feet from residential units[11]. The county says future data center proposals must now obtain special exception approval[1]. In September 2026, NBC4 Washington reported the board voted 7-1-1 to direct staff to draft a resolution pausing data center applications for 12 months[12].

Next door, the largest proposal in the region collapsed in court. Prince William County says the Board’s approvals of the Digital Gateway rezonings are void and the properties revert to their prior zoning[13]; WTOP and InsideNoVa reported a judge ruled in August 2025 that the rezonings were void because of improper public notice before the county’s December 2023 hearing and vote[14]. At full buildout, the Digital Gateway near Gainesville would have been the largest data center campus in the world, with over 22 million square feet across 2,000 acres along Pageland Lane[14].

See every rule we track in the local rules tracker, and the current pauses in the moratorium tracker.

Common questions

What is Data Center Alley?

The eastern part of Loudoun County, Virginia, north of Dulles International Airport, which Virginia’s legislative auditors say became known as Data Center Alley because of its high concentration of data centers. Ashburn is its center.

How many data centers are in Ashburn and Loudoun County?

Loudoun County says there are approximately 233 existing data center buildings totaling about 56.5 million square feet, built or in various stages of construction.

Does 70% of the world’s internet traffic go through Ashburn?

That figure comes from a 2016 Washingtonian report that did not name a source. Loudoun County says only that much of the world’s internet traffic passes through its digital infrastructure.

Can new data centers still be built in Loudoun County?

Not by right. The Board of Supervisors eliminated by-right data center development in March 2025, so proposals need special exception approval, and in September 2026 the board directed staff to draft a resolution pausing applications for 12 months.

Sources

1. Data Centers: The Loudoun Story
   Loudoun County, Virginia · 2026-03
   6 source excerpts

   “There are approximately 233 existing data center buildings, representing approximately 56.5 million square feet, either built or under various stages of the construction process.”

   “In Fiscal Year 2026, data centers generated $1.2 billion in real and personal property tax revenue, representing 39% of the county's overall budget. The FY 2027 adopted budget projects data center revenue at $1.3 billion, representing 40% of the total budget.”

   “Loudoun's data center story began in 1992, when engineers from Metropolitan Fiber Systems and UUNet hooked up local fiber networks in a parking garage in Vienna, Virginia, creating the first commercial Internet Exchange Point (IXP). The IXP was known as the Metropolitan Area Exchange – East, or MAE East, and was in close proximity to Loudoun County.”

   “In 1996, America Online (AOL) opened its global headquarters in Ashburn ... UUNet, another of the world's first Internet Service Providers, subsequently opened its headquarters in Ashburn in 1998”

   “the Zoning Administrator determined that data centers were permitted 'by right' (without any additional legislative approval) in many of these office parks.”

   “Since eliminating 'by right' data center development in 2025, Loudoun County has shifted its focus to strategically managing existing and proposed data centers, requiring future data center development proposals to obtain 'special exception' approval.”

2. Data Centers: Energy Issues & Considerations
   Loudoun County, Virginia · 2026
   2 source excerpts

   “According to PJM, the Regional Transmission Organization serving Virginia, data centers in Loudoun County cumulatively use at least 3 gigawatt (GW) of power at any given time, which is enough to power 2.25 million average U.S. homes.”

   “In northern Virginia, the regional power grid has become strained in large part due to increased electrical demand from data centers over the past 20 plus years.”

3. Data Centers in Virginia
   Joint Legislative Audit and Review Commission (JLARC), Virginia General Assembly · 2024-12
   5 source excerpts

   “The eastern part of the county north of Dulles International Airport has become known as 'Data Center Alley' because of its high concentration of data centers.”

   “Loudoun County alone accounts for approximately half of the state's data center industry in terms of number of sites, building square footage, and estimated energy usage.”

   “The establishment of an internet exchange point in the 1990s further attracted major telecommunications and early internet companies to the region.”

   “80 percent of Virginia's data center industry is concentrated in three Northern Virginia localities: Loudoun, Prince William, and Fairfax.”

   “Loudoun and Prince William have the largest and most mature markets, and data center revenue accounted for 31 percent and 7 percent, respectively, of total local tax revenue (Figure 2-4).”

4. Data Centers
   Loudoun County Economic Development · 2026
   2 source excerpts

   “53.3 million square feet of data centers are currently in operation or under development.”

   “Much of the world's internet traffic passes through Loudoun's digital infrastructure, known as 'Data Center Alley'.”

5. 70 Percent of the World's Web Traffic Flows Through Loudoun County
   Washingtonian · 2016-09-14
   Source excerpt

   “An estimated 70 percent of the world's web traffic—streaming video, financial transactions, NSFW activities—flows through the colorful insides of these windowless buildings.”

6. Data Centers: Tax Revenues & County Budget
   Loudoun County, Virginia · 2026
   2 source excerpts

   “The revenue has enabled the county to generally lower the real property tax rate for homeowners every year for the past decade; the current real property tax rate is the lowest in northern Virginia.”

   “One challenge with managing the vast increase in revenue generated by data centers is that the county must limit the growth in its budget to a level that is sustainable over time and in recognition that the growth of data center personal property tax revenues will plateau in the next five to 10 years at some future point.”

7. Power struggles in Data Center Alley
   Route Fifty · 2022-07-29
   Source excerpt

   “The data center industry has grown substantially in Northern Virginia in recent years, and we've made significant investments to meet the growing demand for electricity. That growth is now accelerating, which is resulting in transmission constraints in a pocket of eastern Loudoun County that primarily serves large customers.”

8. Transmission Lines in Loudoun County
   Loudoun County, Virginia · 2026-09
   Source excerpt

   “the county may file a 'notice of participation' in cases before the State Corporation Commission (SCC), which is the regulatory authority over utilities in Virginia. The SCC is the governing body that reviews and approves the routing of high-voltage transmission line projects prior to construction.”

9. SCC approves Loudoun transmission line, nixes undergrounding; final route to be determined
   Virginia Mercury · 2026-04-10
   Source excerpt

   “After months of fierce debate and community rallies, the State Corporation Commission on Thursday approved the above-ground construction of the Golden-Mars high-voltage transmission line in Loudoun County.”

10. Data Centers in Virginia (Summary)
    Joint Legislative Audit and Review Commission (JLARC), Virginia General Assembly · 2024-12
    Source excerpt

    “An independent forecast commissioned by JLARC shows that unconstrained demand for power in Virginia would double within the next 10 years. ... Building enough infrastructure for unconstrained data center demand will be very difficult to achieve.”

11. By-Right Data Centers Eliminated in Loudoun, Existing Applications Grandfathered
    Loudoun Now · 2025-03-19
    Source excerpt

    “The vote to enact the change passed 7-2 with supervisors Kristen C. Umstattd (D-Leesburg) and Caleb A. Kershner (R-Catoctin) opposed. ... Supervisors also narrowly adopted a grandfathering resolution that exempted data center applications submitted by Feb. 12 for projects that are more than 500 feet away from residential units”

12. Loudoun County board pauses data center applications
    NBC4 Washington · 2026-09-16
    Source excerpt

    “The vote directs board staff to draft a resolution that would pause data center applications for 12 months. It passed 7-1-1, with Supervisor Kristen Umstattd of the Leesburg district voting against it and Supervisor Caleb Kershner of the Catoctin district abstaining.”

13. PW Digital Gateway
    Prince William County, Virginia · 2026-08-05
    Source excerpt

    “The Board of County Supervisors decisions to approve the rezoning of the property are void and the zoning of the properties reverts back to the original zoning district immediately prior to the Board of County Supervisors approval of the rezonings.”

14. Developers drop appeal of zoning decision on Digital Gateway project
    WTOP News (from InsideNoVa) · 2026-04
    2 source excerpts

    “In August, Prince William Circuit Court Judge Kimberly Irving ruled the initial rezonings were void due to improper public notice ahead of the county's December 2023 hearing and eventual vote on the matter.”

    “At full buildout, the Digital Gateway near Gainesville would be the largest data center campus in the world. It would include over 22 million square feet of data centers spread out across 2,000 acres along Pageland Lane.”

Each source was opened and checked against the excerpt shown. Company statements are identified as such. Figures are as published; where sources differ, each is shown.