Theodore Petry (1924-2018) was a laboratory helper at the Chicago Met Lab. He was recruited while still in high school. He helped transport materials for the Met Lab, and was involved with planing graphite blocks and assembling Chicago Pile-1.
He was present on December 2, 1942, when Chicago Pile-1 went critical. For a brief period, he worked as a deckhand on an ore freighter on Lake Michigan. He later worked for the Pullman Company and at the Joslyn Manufacturing Company as an electrician. He also taught shop at Tilden Tech High School. Petry married in 1951, and had four children.
Until his death in 2018, Petry was the last known surviving witness to Chicago Pile-1. For more on Petry, read this Chicago Tribune article, and Washington Post article.