A party was held in his honor Friday at Chicago's main post office. When he began his career, a postal stamp cost 3 cents.
Initially, Neumann was a railroad clerk, sorting mail on a train that ran between Chicago and Nebraska. He went on to become a maintenance supervisor.
Neumann said if his doctors would let him, he'd keep working.
"And the wife really didn't want me to come back," he said. "She likes me around. I don't know why."
Neumann is known around the post office for his mechanical skills, earning him the nickname "MacGyver" after the TV character.