Civil War Medal of Honor Recipient. Born in Ireland, he was a miner from central Pennsylvania's coal region when he enlisted in the Union Army on October 1, 1861. He was then mustered in as a Private in Company F, 48th Pennsylvania Volunteer Infantry, a regiment made up largely of his fellow coal miners. During the course of his subsequent service he was wounded three times - first at the August 1862 Second Battle of Bull Run, then at the May 1864 Battle of the Wilderness, then finally at the June 17, 1864 Battle of Petersburg, Virginia. It was in the past battle he performed his act of bravery that would see him awarded the MOH. He was with his unit as they made an attack on Confederate positions, successfully routing the rebels and sending them in retreat. Private Monaghan chased a group of fleeing Confederates, and captured them single-handedly when he caught up with them. One of the Confederates had the colors of the 7th New York Volunteer Heavy Artillery regiment, which had been captured by the rebel soldiers the previous day, and Private Monaghan returned to Union lines with the flag (his official citation read simply "Recapture of colors of 7th New York Heavy Artillery"). In July 1864 he took part in his regiment's digging of the mine tunnel under Confederate lines that resulted in the explosion on July 30, 1864 and the subsequent disastrous Battle of the Crater. He was awarded his Medal of Honor on December 1, 1864, and it was personally presented to him by Army of the Potomac commander Major General George Gordon Meade. Promoted to Sergeant, he was honorably mustered out on July 17, 1865. After the war he enlisted in the Pennsylvania National Guard, and rose to Lieutenant Colonel of the 7th Regiment before his retirement. His time in the National Guard was marked by their deployment to suppress the "Molly Maguires" and the labor unrest in the coal regions in the 1870s. He passed away at age 72 in Girardville, Pennsylvania n 1917.