On December 12, 1864, President Abraham Lincoln nominated Major Abbott for the award of the honorary grade of brevet brigadier general, United States Volunteers, to rank from August 1, 1864. The United States Senate confirmed the award on February 20, 1865. On February 15, 1867, President Andrew Johnson nominated Major Abbott for the award of the honorary grades of brevet lieutenant colonel, brevet colonel, and brevet brigadier general, United States Army (Regular Army), to rank from March 13, 1865. The U. S. Senate confirmed the awards on March 2, 1867.