Little is known of the life of Willis A. Pomeroy preceding the Civil War. He was the son of Chauncey Pomeroy and Eliza (Granger) Pomeroy and was born in Suffield, Connecticut on March 18, 1841. Pomeroy had two brothers, Chauncey and Arthur, and two sisters, Maria and Cornelia. Willis Pomeroy was married to Mary A. Nixon, but they had no children.
Willis Pomeroy enlisted and was mustered in on May 23, 1861 as a 1st lieutenant with "C" Company, 1st Regiment, Heavy Artillery, Connecticut Volunteers. By June his unit had been shipped to Chambersburg, Pennsylvania. Pomeroy was now a lieutenant with the 4th Connecticut Volunteers, which was attached to the 6th Brigade, 2nd Division of the Army of the Potomac. During June 1861 his unit was moved from Chambersburg to outside of Hagerstown, Maryland. On June 26, 1861 Pomeroy was appointed brigade commissary and aide to General Abercrombie with a promotion to the rank of captain. Captain Pomeroy was then responsible for requisitioning all supplies for the brigade, organizing supply trains, and ensuring that the men of the brigade had enough supplies and ammunition for extended marches. Another of Pomeroy's duties was to accompany General Abercrombie whenever he traveled from his headquarters.
During the latter part of June 1861 the brigade moved to Downsville, Maryland, and then on to Williamsport in July to protect the city of Washington against capture by the rebels. From July 1 to July 30 little is known of Pomeroy's fate except that he was under the care of Dr. Skinner sometime during the month and was residing in Harper's Ferry. It is possible that Pomeroy was wounded because on July 2nd, General Abercrombie, commanding the 6th Bridge, engaged the advance forces of Colonel Johnson and a large force of cavalry under Jeb Stuart near Falling Waters, Virginia.
Pomeroy was ill enough, however, to consider resigning his commission. He was on furlough for most of August and September 1861, probably convalescing. When Pomeroy returned to active duty in the latter part of September, he was transferred to the 2nd Brigade of General Banks's division, which was stationed at Camp Lyon in Darnestown, Maryland. This unit was to be moved to a fort outside Washington, D. C., as part of an artillery regiment.
Willis Pomeroy resigned his commission on November 7, 1861. He died August 17, 1867 in Suffield, Connecticut.