>>14
Well the Thirteenth Amendment officially abolished slavery. And eventually something had to be done about the slave issue that was facing the still quite young nation at the time.
That's the great thing about the Constitution is that it can be amended and expanded upon, and the founders very well knew that slavery would probably become a big issue past their lifetimes. Thomas Jefferson touches upon this in some of his writing.
Of course future amendments can bring bad effects too, see the Sixteenth and Seventeenth Amendments, that allowed the IRS to tax income and the Seventeenth which changed how Senators are elected, chipping away at state sovereignty.