Which famous humorist was also a steamboat captain on the Mississippi?

Mark Twain, the famous humorist, is well-known not only for his literary contributions but also for his early career as a steamboat captain on the Mississippi River. His experiences on the river greatly influenced his writing and provided rich material for his novels and stories, particularly in works like "Adventures of Huckleberry Finn" and "The Adventures of Tom Sawyer." The steamboat industry was a significant part of American culture in the 19th century, and Twain's firsthand encounters with the river and its navigation helped shape his understanding of the themes of adventure and the complexities of human nature that permeate his literature.

In contrast, George Washington Cable was a notable author and social critic who focused on the culture and lifestyle of Louisiana but did not serve as a steamboat captain. Oscar Dunn was an important political figure in Louisiana’s history and the first African American elected to statewide office in the South after Reconstruction, but he did not have a career tied to river navigation. Norbert Rillieux was a pioneering engineer known for his innovations in sugar processing, again unrelated to the steamboat industry. Thus, Mark Twain stands out as the individual who combined humor with the life of a river captain, making him the correct answer.