He was one of the founders of the Delta Psi fraternity at the University of Vermont,[6] and in early life was an active member of the Masons, Odd Fellows, Sons of Temperance, and the International Order of Good Templars, having been presiding officer in each, as also in various county and state teachers' organizations, and later in the Grand Army of the Republic, from which body he was a delegate-at-large from Vermont at the twenty-fifth national encampment at Detroit in August 1891.

[8] On 14 September 1853 Abel Edgar Leavenworth was married to Mary Evelina, daughter of Samuel and Sally (Hubbard) Griggs, of Cazenovia, New York.

Following her death, Abel Edgar Leavenworth married Lucy Elizabeth, daughter of Marcus N. and Julia M. (Burt) Wadsworth, of Oswego, New York.

Abel E. Leavenworth was a veteran of the American Civil War, and soon after his enlistment as a private in Company K, Ninth Regiment Vermont Volunteers, was promoted through the ranks of sergeant and first lieutenant to that of captain.

He also served as assistant adjutant general of the last named command, later of the Second brigade, Third division, Twenty-fourth army corps, and led the skirmish line into the city of Richmond on 3 April 1865.