Episcopal (Church of England). Until 1785 all Virginians were required to support and attend the Church of England.

• Hamilton Parish was established in 1730 from Overwharton Parish (Stafford County) and Hanover Parish (King George County). It covered the whole area that became Prince William County in 1731. Truro Parish, north of Occoquan River, was cut off in 1732 (the area that became Fairfax County in 1742). Dettingen Parish, the eastern region, was cut off in 1745. After 1759, when Fauquier County was created, only a small portion of Hamilton Parish remained in western Prince William. In 1769, the northern part of Hamilton Parish was cut off to make Leeds Parish. Of these parishes, only Overwharton has a colonial register of births, marriages and deaths (1723-1758). The few entries with dates back to 1723 (births only) appear to have been recorded after 1738, when Prince William’s territory was no longer part of the parish.
• Pohick Church. Minutes of the Vestry, Truro Parish Virginia, 1732-1785 (1974). Truro Parish was within Prince William County until 1742. It is now within Fairfax County. No register survives.
• Records of Dettingen Parish, Prince William. County, Virginia: vestry book 1745-1782, minutes of overseers of the poor 1788-1802, indentures 1749-1782 (1976). Business records of the parish. [HD]
• Library of Virginia has Dumfries Church register 1815-1824 (Dettingen Parish). Its marriages were published in Magazine of Virginia Genealogy, v.24 (Feb. 1986); membership and baptisms in Virginia Genealogist, v.30 (Apr.-June 1986).
• Naisawald, L. VanLoan. Trinity Episcopal Church 1872-1972, Dettingen Parish, 1744-1972 (1972).
• St. Paul’s Episcopal Church, Haymarket, Virginia: 150th anniversary, August 1984.
• St. Paul’s Episcopal Church, Haymarket, Virginia, parish records 1837-1995 (1996). [PWGS]

Baptist. Library of Virginia has records of the four earliest Prince William churches.

• Broad Run Church 1762-1873 (served Fauquier and western Prince William). Records 1762-1783 published in Magazine of Virginia Genealogy, v. 26 (Nov. 1988).
• Chappawamsic Church 1766-1919 (served southern Prince William and northern Stafford). Records 1766-1844 published in Magazine of Virginia Genealogy, v. 27 (Feb.-Aug. 1989).
• Frying Pan Church 1791-1879 (served northern Prince William, along with eastern Loudoun, western Fairfax). RELIC has microfilm.
• Occoquan Church 1794-1843 (served eastern Prince William). Membership lists published in Northern Virginia genealogy, v. 2 (Apr. 1997).
• Cardwell, Cora Lee. Following the dream: the history of Manassas Baptist Church 1884-1984 (1983).

Source: Prince William County Relic Room
http://www.co.prince-william.va.us/library/relic/geneal.htm