How was Reconstruction a failure?

Reconstruction was a failure in that it failed to ensure
civil liberties for former slaves or provide a life for them which came anywhere close
to equality.

Slavery was ended by the Thirteenth Amendment
(NOT, contrary to popular myth, by the Emancipation Proclamation.) However, once freed,
slaves had no means of providing for themselves or their families or of ensuring
equality of treatment. Congress attempted to remedy this first by creating the
Freedman's Bureau and also by passing the Fourteenth Amendment which presumably gave
them the equal protection of the law and the Fifteenth Amendment which presumably gave
them the right to vote.

Both Amendments were circumvented
with abandon. The U.S. Supreme Court in Plessy vs. Ferguson in
1896 sanctioned "separate but equal" facilities. it was not until 1954 with
Brown vs. Board of Education that the heinous doctrine of "separate
but equal" was abrogated. Southern states imposed poll taxes, literacy and residency
requirements, among others to keep blacks from voting, and also listed certain crimes
assumed to be common among Blacks (wife beating, public drunkeness, etc.) as
disqualifications for voting. Vigilantes such as the Ku Klux Klan terrorized Blacks to
prevent their exercising their rights as U.S. citizens. Rather than deal with these
injustices, Congressional Republicans agreed to withdraw troops from the South in 1877
to ensure the election of their candidate, Rutherford B. Hayes, to the White House.
Reconstruction was left only partially completed, and true rehabilitation did not occur
for another one hundred years.