John Dunn (ca. 1750-1827) married Elizabeth Marye (ca. 1774-1851) a daughter of the the Reverend James Marye (1731-1780). She was a granddaughter of the Reverend James Mayre, (d. 1767), a Huguenot refugee, and Letitia Maria Ann Staige (d. 1739). The first Bishop of the Episcopal Diocese of Virginia, James Madison (1749-1812), ordained Dunn an Episcopal priest. Dunn served in St. John's Parish, King William County (ca. 1797), Manchester Parish, Chesterfield County (ca. 1799) and Shelburne Parish (St. James Episcopal Church, Leesburg), Loudoun County (1801-1827). He served as a member of the Standing Committee of the Diocese of Virginia up until his death. There being no Episcopal church building in Leesburg during the years 1801-1812 Dunn celebrated services in the Old Presbyterian Church and the Clerk's office. In Middleburg he celebrated services in the Free Church. In April 1827, Dunn suffered paralysis while performing a service in Middleburg, was moved to Leesburg, where he died shortly thereafter. Dunn was buried under the floor of the old St. James Episcopal Church chancel over which a memorial monument was erected by the congregation. According to the Loudoun Cemetery database Dunn is buried in the Old Episcopal Church Cemetery, Leesburg, Virginia.

John Dunn was an active member of the fraternity of Free and Accepted Masons and a member of the Olive Branch and United Brethren Lodges in Leesburg. According to advertisements and articles in the Genius of Liberty, 1818-1820, the Olive Branch and United Brethren Lodges, annually celebrated the feast of St. John the Baptist and St. John the Evangelist to whom their lodges were dedicated. The Reverend John Dunn preached the sermon for this celebration in 1818 and 1819. In 1818 the presentation was adapted from the text, Hebrews XIII.1 "Let brotherly love continue."