(1834 - 1863)
Home State: Pennsylvania
Command Billet: Commanding Regiment
Branch of Service: Cavalry
Unit: 8th Pennsylvania Cavalry
He lived in Philadelphia at the start of the War, and in the summer of 1861 helped recruit the 8th Pennsylvania Cavalry. He was appointed Captain, Company C, 19 August 1861.
The rest of the War
He was promoted to Major of the regiment 15 October 1862. According to the Pleasonton version, at the Battle of Chancellorsville, "he was ordered by General Alfred Pleasonton, after the rout of the 11th corps on the right wing, to charge the advancing enemy in a wood, and hold them in check until the artillery could be got into position. He charged with his regiment, which numbered fewer than 500 men, so impetuously that the Confederates were startled, and hesitated to advance from the wood, until the guns were ready to rake the column as it emerged. Keenan met an inevitable death at the head of his men, many of whom fell with him, but the sacrifice enabled General Pleasonton to hold Stonewall Jackson's corps in cheek and save the army from rout."
More recent scholarship suggests that Major Keenan and his troopers ran into Jackson's infantry by accident, and were cut down in surprise (see Krick).
References & notes
Sources: Appleton's Cyclopedia of American Biography, edited by James Grant Wilson and John Fiske. Six volumes, New York: D. Appleton and Company, 1887-1889; and
Krick, Robert K., Chancellorsville: Dusk, lies, and cavalry, an online article on fredericksburg.com, from The Free Lance-Star Publishing Company; and
Bates, Samuel P., Martial Deeds Of Pennsylvania, Philadelphia: T. H. Davis & Co., 1876 transcribed online by the Pennsylvania USGenWeb Archives
11/9/1834; York, NY
5/2/1863; Chancellorsville, VA