"The Drummer Boy of Chickamauga" was 12 years old when he was promoted to sergeant after firing on a Confederate colonel who was attempting to capture him. At that point John Lincoln Clem became the youngest non-commissioned officer in U.S. history and a Civil War hero.
2nd Lt. John Lincoln Clem Photo: Library of Congress
In 1870, Clem attempted to enter West Point but failed the entrance exam multiple times. President Ulysses S. Grant commissioned Clem as a second lieutenant in 1871, ignoring the fact that Clem couldn't pass the tests.
Clem went on to serve until 1915, mostly as an Army quartermaster. He was the last Civil War vet still on active duty when he retired as a brigadier general.