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.

Manassas (; formerly Manassas Junction) is an independent city in the Commonwealth of Virginia. As of the 2010 census, the population was 37,821. The city borders Prince William County, and the independent city of Manassas Park, Virginia. The Bureau of Economic Analysis includes both Manassas and Manassas Park with Prince William County for statistical purposes. Manassas also serves as the seat of Prince William County. It surrounds the 38-acre (150,000 m2) county courthouse, but that county property is not part of the city. The City of Manassas has several important historic sites from the period 1850–1870. The City of Manassas is part of the Washington-Arlington-Alexandria, DC-VA-MD-WV Metropolitan Statistical Area and is in the Northern Virginia region.

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.

Rappahannock County is a county located in the northern Piedmont region of the Commonwealth of Virginia, US, adjacent to Shenandoah National Park. In 2019, the population was estimated to be 7,370. Its county seat is Washington. The name "Rappahannock" comes from the Algonquian word lappihanne (also noted as toppehannock), meaning "river of quick, rising water" or "where the tide ebbs and flows." The county is included in the Washington-Arlington-Alexandria, DC-VA-MD-WV Metropolitan Statistical Area.