What problems with the original Constitution, or changes in society, led to the 13th through 15th amendments.

The change in society that led to the 13th through 15th
Amendments was the Civil War.  Because of the Civil War, the people of the North felt
that it was necessary to pass these amendments, which are collectively known as the
"Civil War Amendments."

At the time the Constitution was
written, slavery formed the basis of the Southern economy and had to be accomodated in
order to get the South to ratify the document.  The differences between the slave South
and the free North eventually led to the Civil War.  After that war, the North did not
want the South to go back to having the "peculiar institution" that had been the cause
of the sectional animosity.  Because of this, the North felt it was important to amend
the Constitution to end slavery and to give freed blacks rights that were at least
officially equal to those of whites.