Slavery and Racism.
The main issue is trying to free Jim, a slave, from slavery. Huck and Tom help each other free Jim from Slavery. Jim wasn't treated badly by his owner, Miss Watson, but he still didn't want to be owned. Jim has wife and kids and because he is a slave he is unable to see them. Huck tries to free Jim. At first Huck hesitates at the thought of taking Jim from Miss Watson seeing as how she took care of him but because Jim is a really good friend to him he's sees it as doing a friend a really huge favor.
