How was the American Reconstruction Period considered a success?

Overall it was considered a failure, but that didn't mean
there weren't parts of it that were successful.

For one
thing, the Reconstruction Era from 1865-1877 successfully amended the Constitution not
once, but three times.  Slavery was permanently and formally ended, freed slaves were
given citizenship and black males over 21 the right to vote.  This could never be
legally taken away, although it was delayed and discouraged for a long
time.

The Freedman's Bureau constructed schools for freed
slaves and send 1500 volunteer teachers into the South to run them.  Over the course of
six and a half years, the Freedman's Bureau taught over 200,000 freed slaves to basic
literacy.  While most were still left untaught, that is a staggering number to be
accomplished in such a short time.

Lastly, they did come up
with a way to legally get the southern states back in the Union, and in a way they would
agree to, when they adopted Lincoln's 10% Plan.  This made it very easy for them to
reapply for statehood and to send Senators and Representatives to Congress once
again.