Prince William County is located on the Potomac River in the Commonwealth of Virginia in the United States. As of the 2010 census, the population was 402,002, on July 1, 2019, the population was estimated to be 470,335, making it Virginia's second-most populous county. Its county seat is the independent city of Manassas.A part of Northern Virginia, Prince William County is part of the Washington metropolitan area. In 2019 it had the 20th-highest income of any county in the United States.

The City of Fairfax ( FAIR-faks), colloquially known as Fairfax City, Downtown Fairfax, Old Town Fairfax, Fairfax Courthouse, or simply Fairfax, is an independent city in the Commonwealth of Virginia in the United States. As of the 2010 census the population was 22,565, which had risen to an estimated 24,019 as of 2019.The City of Fairfax is an enclave surrounded by the separate political entity Fairfax County. Fairfax City also contains an exclave of Fairfax County, the Fairfax County Court Complex. The City of Fairfax and the area immediately surrounding the historical border of the City of Fairfax, collectively designated by Fairfax County as "Fairfax", comprise the county seat of Fairfax County. The city is part of the Washington–Arlington–Alexandria, DC–VA–MD–WV Metropolitan Statistical Area as well as a part of Northern Virginia. The city is 17 miles (27 km) west of Washington, D.C. The Washington Metro's Orange Line serves Fairfax through its Vienna station, which is a mile northeast of the city limits. CUE Bus and Metrobus operate in Fairfax. Virginia Railway Express's Burke Centre station is situated three miles southeast of the city's boundaries. Virginia's largest public educational institution with 35,189 students in 2017 is George Mason University, which is located in unincorporated Fairfax County, along the city's southern border while still having a City of Fairfax address and sharing the same public transportation system.

Fauquier is a county in the Commonwealth of Virginia. As of the 2010 census, the population was 65,203. The county seat is Warrenton.Fauquier County is in Northern Virginia and is a part of the Washington metropolitan area. The county is one of the fastest-growing and highest-income counties in the United States.

Middleburg is a town in Loudoun County, Virginia, United States, with a population of 673 as of the 2010 census. It is the southernmost town along Loudoun County's shared border with Fauquier County. Middleburg is known as the "Nation's Horse and Hunt Capital" for its foxhunting, steeplechases, and large estates. The Middleburg Historic District, comprising the 19th-century center of town, is listed on the National Register of Historic Places.