Scanned from a negative from 1939
Two men looking at the Pennsylvania Railroad S1 locomotive at the New York World's Fair.
The S1 was built in 1939 and taken to the fair after initial testing, at the Fair it was mounted on rollers so the engine could be run in place.
After the Fair closed the S1 entered operational service, it's large size limited the tracks that it could run on, particularly curves. It was retired in 1946 and scrapped in 1949.