On journeys ranging from two nights to two weeks the Delta Queen cruises American rivers eleven months of the year; many of her trips are tied to themes or special events, such as the Kentucky Derby. For schedules and prices call the Delta Queen Steamboat Company, 800-543-7637. Its second vessel, the Mississippi Queen , commissioned in 1976, is the largest overnight paddle-wheeler ever built, a Victorian-style confection, with such modern touches as an elevator, a beauty salon, and a swimming pool. Like the Delta Queen , she is propelled by a paddle wheel and entirely powered by condensing steam engines fueled by a mixture of steam and oil. Recently the company announced plans to built a third boat.