City and port on the Mississippi River in Missouri, US; boyhood home of Mark Twain (8)

(Other definitions for hannibal that I've seen before include "Carthaginian general who crossed the Alps to defeat Rome" , "Carthaginian general who fought Rome" , "Carthaginian general who crossed Alps to attack Rome" , "Famous general who crossed the Alps with elephants and defeated the Romans" , "Great Carthaginian general who led army over the Alps against Rome" .)