Brentsville was the fourth seat of the Prince William County government. Its courthouse, jail, Episcopal Chapel, and White House were built in 1822 on land originally part of the Brent Town tract, which had been confiscated from Robert Bristow, a Tory, in 1779. St. James Church of Dettingen Parish, now Hatcher’s Memorial Baptist, was built in 1847 on the site of the old chapel. During the War Between the States, Col. Mosby operated in this area. In 1893 the county seat was moved to Manassas.