Enlisted 24 May 1862 (credited to Brattleboro, VT), mustered as 1st Sgt. in Co. K 9th Vermont Infantry 9 Jul 1862, commissioned 1st Lt. 17 Nov 1862, promoted to Capt. 1 Dec 1864, appointed Provost Marshall of Richmond 5 Apr 1865, mustered out 13 Jun 1865.

Source:
http://vermontcivilwar.org/

Following Provided by member #47283828

From: Men of Vermont: An Illustrated Biographical History of Vermonters and Sons of Vermont. BIOGRAPHIES OF VERMONTERS A. D. 1892-93 avail on ancestry.com.

Leavenworth, Abel Edgar,of Castleton, son of Abel and Anna (Hickok) Leavenworth, was born in Charlotte, Sept. 3, 1828.
Having obtained his preparatory education at the district schools of Madrid, N. Y., and Charlotte, he continued his studies at Hinesburgh Academy, and afterwards entered the University of Vermont, from which he graduated in 1856, on his return from the South.
He commenced his career as a teacher in 1846, taught district schools five winters and became successively the principal of Bolivar (Mo.) Academy, and the academies of Hinesburgh, Brattleboro and New Haven. In 1870 he secured the incorporation and endowment of Beeman Academy at New Haven, the position of principal of which, after a most successful administration, he resigned in 1874 to become principal of the State Normal School at Randolph, leaving the former institution with an endowment fund of twelve thousand dollars. Leaving the Normal School at Randolph in 1879, after having greatly increased its facilities and the number of the pupils, he spent two years in institute work and the collection of a large and choice cabinet of minerals, while recruiting his impaired health. In 1881 he purchased the school building and equipment of the Rutland county grammar school, and was appointed principal of the State Normal School at Castleton under its patronage. Since that date Mr. Leavenworth has devoted his energies to the interests of the school, and has always given special attention to the training of teachers, having signed six hundred and thirty-nine certificates while principal of the various institutions under his charge.
Mr. Leavenworth is a veteran of the civil war, and soon after his enlistment as a private in Co. K, 9th Regt. Vt. Vols., was promoted through the ranks of sergeant and 1st lieutenant to that of captain. He was made assistant inspector general of Wistar's brigade of the United States forces on York Peninsula, of the 2nd division of the 18th army corps, and of the provisional brigade at Bermuda Hundreds. He also served as [p.244] assistant adjutant general of the last named command, later of the 2d brigade, 3d division, 24th army corps, and led the skirmish line into the city of Richmond, April 3, 1865. He was appointed assistant provost marshal of that city and subsequently assistant adjutant general of the district of Appomattox. He was mustered out of the service at Richmond, June 13, 1865, having received highly commendatory letters from the generals on whose staff he had served.
Mr. Leavenworth was married at Corning, N. Y., Sept. 14, 1853, to Mary Evelina, daughter of Samuel and Sally (Hubbard) Griggs of Cazenovia, N. Y. To them were born: Anna Maria (deceased), Francis Abel (deceased), Samuel Edgar, Clarence Greenman, William Stowell, Emily Reynolds (deceased), and Philip Reynolds. Mrs. Leavenworth died July 30, 1877, and he contracted a second alliance at Linden, Md., August 12, 1889, with Lucy Elizabeth, daughter of Marcus N. and Julia M. (Burt) Wadsworth of Oswego, N. Y.
At the age of twelve he united with the Congregational church, with which he has continued his connection, serving the local congregation as deacon and delegate to county associations and state conventions. Never sectarian in belief or practice, he has ever maintained most friendly relations with all branches of the Christian church.
He was one of the founders of the Delta Psi fraternity in the U. V. M., and in early life was an active Mason, Odd Fellow, Son of Temperance, and Good Templar, having been presiding officer in each, as also in various county and state teachers' organizations, and later in the Grand Army, from which body he was a delegate-at-large for Vermont at the twenty-fifth national encampment at Detroit, in August, 1891. He has also been a member of the American Academy of Political and Social Science from the first year of its organization.