Early War view of Kingsbury as Lt in the Regulars.  Civil War Union Army Officer. He graduated from the United States Military Academy at West Point, New York in May 1861, and was posted as a 1st Lieutenant in the 5th United States Regular Artillery. From June to December 1861 he served as an acting Aide-de-Camp on the staff of Major General Irvin McDowell. On April 25, 1862 he was commissioned as Colonel and commander of the 11th Connecticut Volunteer Infantry, which he led through to the September 17, 1862. In that battle he was killed in action while leading his men against Confederate positions at the Burnside's Bridge area. He was interred in Oak Hill Cemetery, Washington, DC, and a cenotaph was erected for him in the North Lyme Cemetery, Lyme, Connecticut.