How was abraham lincoln responsible for the unification of the united states?

Are there any answer choices? That would help. 
But Abraham Lincoln was instrumental in unifying the North and South in the United States. He fought to end slavery and to keep the South in the Union.

Yes, some people used the depression to the max. not everybody had stocks, and those that didn't bought many things inexpensive, so that when prices rose again, they were much more richer than beforehope this