When Captain John Smith and other English explorers came to the upper Potomac beginning in 1608, they reported that the area within present Prince William County was occupied by the Doeg tribe. The Doeg Indians maintained several villages in this area into the 1650s, when colonists began to patent the land.
Prince William County was created by an act of the General Assembly of the colony of Virginia in 1731, largely from the western section of Stafford County as well as a section of King George County. The area encompassed by the Act creating Prince William County originally included all of what later became Arlington County, the City of Alexandria, Fairfax County, the City of Fairfax, the City of Falls Church, Fauquier County, Loudoun County, the City of Manassas, and the City of Manassas Park (and the various incorporated towns therein). The County was named for Prince William, Duke of Cumberland, the third son of King George II.
The County was a rural community for years and the population was centered in two areas, one at Manassas (home to a major railroad junction), the other near Occoquan and Woodbridge along the Potomac River. Beginning in the late 1930s, a larger suburban population grew up near the existing population centers, particularly in Manassas. Beginning in the late 1960s, the County and its population expanded dramatically to the point where, by the end of the 20th century, it was the third most populous local jurisdiction in Virginia. Much of this growth has taken place in the last twenty years. Recently Prince William County has seen the opening of the Marine Corps Heritage Museum, the Hylton Performing Arts Center, the announcement of the coming American Wartime Museum and the 150th commemoration of the Sesquicentennial of the Civil War and the famous First and Second Battles of Manassas.
Information and images courtesy of wikipedia.com