Sergeant Maupin was a member of the 25th Reconnaissance Company, 25th Infantry Division. He was listed as Missing in Action while fighting the enemy in South Korea on 3 January 1951. He was presumed dead on 31 December 1953. His remains were not recovered. His name is inscribed on the Courts of the Missing at the Honolulu Memorial.

Maupin was awarded the Purple Heart, the Combat Infantryman's Badge, the Korean Service Medal, the United Nations Service Medal, the National Defense Service Medal, the Korean Presidential Unit Citation and the Republic of Korea War Service Medal.