This is from Wikipedia and Home of the Hero’s.

William “Willie” Johnston
 

William “Willie” Johnston (born July 1850), from St. Johnsbury, Vermont, was a drummer boy in Company D of the 3rd Vermont Infantry. His service during the Seven Days retreat in the Peninsula Campaign was exemplary. He was the only drummer in his division to come away with his instrument, by no means a trivial accomplishment. As a result, he received theMedal of Honor on the recommendation of his division commander, thereby becoming the youngest recipient of the highest decoration at 13 years of age.[1][2]

Johnston was born in Morristown, New York in 1850. Apparently his family moved to Salem, Vermont (now Derby). When his father enlisted in December, 1861, young Willie begged to go with him. The commanding officer agreed. He was enlisted as a drummer boy on December 11, 1861 in St. Johnsbury, Vermont. He was 11 years old and five feet tall.[3]

Johnston’s first fight was at Lee’s Mill, Virginia, on April 16, 1862.
During his next campaign, the Seven Days Battles from June 25 to July 1, 1862, Johnston was cited for bravery.
During that retreat many men threw away all their equipment so they would have less weight to carry. Johnston, however, retained his drum and brought it safely to Harrison’s Landing. There, he had the honor of drumming for the division parade, he being the only drummer boy to bring his instrument off the battlefields. Johnston’s division commander noted this fact and included them in his report. President Lincoln heard the story and wrote Secretary of War Edwin M. Stanton, suggesting the youth be given a medal. Stanton agreed, and Willie Johnston was presented his Medal of Honor September 16, 1863, at the age of 13, for a deed performed when he was but 11 years of age.[4]
This was the second Medal of Honor ever awarded. Secretary Stanton presented the actual award.

Medal of Honor citation


Original Army Medal of Honor
The President of the United States
in the name of
The Congress
takes pleasure in presenting the
Medal of Honor
to
JOHNSTON, WILLIAM “WILLIE”

Gallantry in Seven Day Battle and Peninsula campaign.