The marriage was by Thomas Birkby (Methodist Episcopal.) From Genius of Liberty newspaper:
Vol. V, No. 1 – January 16, 1821
Married January 4 by Thomas Birkby, John R. Anderson and Abby Thomas, both of Loudoun.
From "Index to Loudoun Co Land Deed Books, 3E-3M, 1822-1826" by Pat Duncan:
Date: 3 Apr 1823
Received in court: 14 Aug 1823
Thomas LEONARD dec’d. Division – Lot #1 (3a) to widow, Lot #2 (1a) to Elizabeth THOMAS, Lot #3 (1a) to Martha THOMAS, Lot #4 (1a) to Anne THOMAS, Lot #5 (1a) to Sarah THOMAS now FEICHTER, Lot #6 (1a) to Abby THOMAS now ANDERSON. Gives plat. Divisors: Daniel LOVETT, Thomas CARR.
Date: 24 Sep 1823
Received in court: 24 Sep 1823
John R. ANDERSON & wife Abby of Loudoun to John Gill WATTS of Ldn. B/S of Abby’s 1a share (lease of Aug 1798 from James HEREFORD to Patrick CAVANS, memo of Jan 1803 said to divide land, assigned to Leonard THOMAS who has now departed intestate leaving a wife and several children, including Abby). Wit: John McCORMICK, John H. McCABE. Delv. to WATT on ___.