Clem not the last officer on active duty
Clem was not the last Civil War Union veteran on active duty - in 1917 Peter Conover Hains was recalled to active duty by special act of Congress and appointed a major general in charge of an Engineering District in Virginia. He was the only Civil War officer to serve in World War I, and at the age of 76, was the oldest United States officer in uniform at the time. A graduate of the United States Military Academy in 1861, Hains served as chief engineer of the XIII Army Corps during the Siege of Vicksburg. After the war he remained in the army, and designed lighthouses at Morris Island and St. Augustine, and designed and built the tidal basin in Washington D.C. During the Spanish American War he served as a brigadier general of volunteers. He died Nov. 7, 1921, and is buried in Arlington National Cemetery.