Rev. Addison then became the first priest that Bishop Claggett ordained after his own consecration as Bishop of Maryland in 1793. Rev. Addison thus succeeded his uncle by serving from 1793 to 1795 as rector of Queen Anne Parish, with its two widely separated churches,
Holy Trinity and
St. Barnabas'. Rev. Addison soon established a school at his home, Oxon Hill. In 1799 he became assistant rector under Rev. Henry T. Addison, and in 1805 he became rector of
St. Matthew's Church, also known as Addison Chapel to commemorate its founder (and both Rev. Addisons' ancestor), Col. John Addison. The current building was erected between 1809 and 1816, under Rev. Walter Addison's direction. Rev. Addison, who freed the slaves he inherited, publicly advocated the abolition of slavery as well as the practice of dueling. He also helped found several Episcopal churches in the new city of Washington, D.C. and Alexandria, Virginia, as well as a black Methodist church in Oxon Hill. Due to the shortage of Episcopal priests in that era and area, while serving at Addison Chapel, in 1801 Rev. Addison also became the first rector of St. John's Church in
Georgetown. Rev. Addison officiated at the funeral of
George Washington. At the end of the year, December 12, 1810, Rev. Addison was appointed as U.S. Senate Chaplain, succeeding Rev.
Obadiah Bruen Brown. Rev. Addison helped incorporate the Georgetown Lancaster School Society, and also served as vice-president of the
Bible Society of the District of Columbia. ==Personal life==