In the 1840s, common food staples included corn bread, pork, beans, and vegetables grown locally, with meat, pastry, and oysters being common in restaurants, while seasonal fruits and vegetables were enjoyed when available.
Huck Finn would most likely have had a diet that looked a little less diverse due to the time period, his location, and social class.
Here is a short article with a brief overview on Missouri's cooking and culinary history.
Corn dodgers are small, fried or baked corn cakes, made with simple ingredients like cornmeal, water, salt, and sometimes bacon fat or butter. They originated as a survival food for pioneers and have a reasonably bland flavor profile and can be eaten with maple syrup to make it taste better.
"Fart and Dart Beans," also known as "Cowboy Beans," are a hearty and flavorful dish of beans, bacon, and other ingredients, popular in the American West. An easy quick dish popular at the time in Missouri especially.
Catching catfish and eating them is mentioned as a staple of Huckleberry Finn's diet in the book, here's a short video of how catfish might have been prepared in the book.
Fun fact: Catching catfish is called "noodling", you stick your arm into catfish holes (where they live) and try to get them to eat your arm so you can pull them out and catch them. Catfish have teeth and real noodlers do it bare handed, ouch!