Use of a Child Protagonist

Hello everyone,

I just finished reading Huckleberry Finn, and in a few weeks, we are required to write a paper about it. It's a literary analysis, and my teacher assigned me the following question: In Huckleberry Finn, the protagonist (Huck Finn) is a child. Why did Mark Twain decide to use a child as opposed to an adult protagonist?

Any ideas?

-Desmond
Tacoma, WA