Donald B, originally Standard, and now Barbara H is a paddlewheel towboat that has been named a US National Historic Landmark and is now based at Lamb, Indiana, across the Ohio River from Carrollton, Kentucky. She is owned by the Historic Sternwheeler Preservation Society, a not-for-profit corporation.
The boat measures 99 feet (30 m) long overall (80 feet (24 m) hull length plus the paddlewheel) by 18 feet (5.5 m) beam. She draws 32 inches (0.8 m). She is powered by a 160 horsepower (120 kW) 1940 Fairbanks-Morse 35E10 direct reversing diesel engine. She measures 51 gross registry tons and displaces approximately 108 long tons (110 t).