Mark Twain Childhood Home and Museum: This multi-building attraction, which marked its 100th anniversary in 2012, is the must-see attraction in Hannibal. The complex includes an interpretive center, which provides detailed background information about Samuel Clemens' life, with snippets of his autobiography used throughout the displays and an informative and humorous film. Twain was quite funny, after all. (Note: The film is long, and there are only two benches for sitting while watching.) You can also visit Clemens' boyhood home; the Huckleberry Finn house where the "real" Huck Finn, Tom Blankenship, grew up; the Becky Thatcher House, home of Laura Hawkins, the inspiration for Becky; and the Mark Twain Museum, with its collection of Clemens family artifacts and 15 Norman Rockwell paintings.
Mark Twain Caves: Located some two miles out of town, these are the same caves Samuel Clemens explored as a child, and they appear in his "Adventures of Tom Sawyer and Huckleberry Finn" books, as well. You can take a 55-minute tour of the caves, now on the Registered National Natural Landmarks list. Nearby, you'll find the Cave Hollow West Winery.
Rockcliffe Mansion: Built in 1898 by a lumber baron, the mansion is listed on the National Register of Historic Places. Inside, you'll find interiors decorated in the Late Victorian and Art Nouveau styles; almost all the furnishings on display are originals. It's open to the public from March 15 through November 15.
Molly Brown Birthplace and Museum: The small cottage in which Molly Brown -- the "unsinkable" socialite, who famously survived the Titanic -- grew up is just a few blocks from downtown. Inside, you'll find displays on her life in Hannibal and beyond, plus a room about Titanic. It's open daily, Memorial Day through Labor Day.