The hook is the most important part of your essay, it catch attention and makes people want to stay and read it, so it's very important and has to be good.
Things you could use:
Make it dramatic and about how lives changed forever in this point in history
Or make it about how things were before the Civil War and how they drastically changed right before.
Or the cause of the civil war, but simplified.
Talk about the states in different views. The war was about slavery, and the southern and northern states had different views
There are many others, but these are what came to mind, the more dramatic, the more interesting.
Best of luck!!