Elevator Key

From the Super Mario Wiki

The Elevator Key is a small Key found in Riverside Station during the events of Paper Mario: The Thousand-Year Door. Mario must retrieve it in order to operate the elevator in the front room of that station – the elevator will then take him to the switch that lowers the drawbridge that is delaying the train. This key was seemingly hidden by the Smorgs to stop and slow down Mario in his mission.

Keys
Black Key | Blue Key | Card Key | Castle Bleck Key | Elevator Key | Fortress Key | House Key | Key | Odd Key | Palace Key | Pedestal Key | Random House Key | Red Key | Ruins Key | Shop Key | Skeleton Key | Station Key | Steeple Key | Storage Key | Storeroom Key | Warehouse Key | Yakkey