Cincinnati Union Terminal opened in 1933.
The terminal began emergency operation on March 19, 1933, when an Ohio River flood forced the closure of four existing Cincinnati stations. Its formal dedication and ceremonial opening followed on March 31, 1933. That distinction explains why both dates appear in historical accounts, while 1933 remains the single canonical answer to the quiz question.
Built to replace five local stations serving seven railroads, Union Terminal was a vast transportation project. Construction began in 1928, and the complex ultimately included the main station, railroad facilities, viaducts, mail and express buildings, and extensive track. The final design by Fellheimer & Wagner became a celebrated example of Art Deco architecture.
Passenger use initially lagged because the Great Depression reduced travel, then rose sharply during World War II. After postwar rail decline, regular passenger service ended in 1972. The building later became the Cincinnati Museum Center, and Amtrak service returned in 1991.
Thus 1935, 1940, and 1929 are incorrect: 1929 marks the start of construction on the terminal building, not its opening.