ways and believed that the Confederacy was a noble cause dedicated to the protection of states' rights.

That being the case, the South was never going to be reconciled to a policy that represented the complete antithesis of just about everything it believed in. And so Reconstruction had to rely on sufficient political energy from Washington, something that was impossible to sustain over the long term.

The point of emphasis of reconstruction after the Civil war was to help black Americans become equal citizens. This obviously met with a lot of resistance from groups in the south. While laws were put into place to give rights to the former slaves the southerner's did not agree with them or abide by them.

I would say that Reconstruction has to be considered somewhat lacking in that the issue of how White America dealt with Black America was never quite resolved.  The fundamental issue of Reconstruction involved attempting to bring together the Northern and the Southern states.  Yet, underlying all of this was the fundamental issue of the "color line."  This was a reality that was never quite fully understood at the time and its premise was never quite dealt with from a governmental standpoint.  The fact that segregation practices became common in the South only proved to exacerbate the regional tension between both.  In not being able to fully dissolve and eradicate this particular fear, Reconstruction has to be seen as something that had more problems to solve that weren't solved than more deliverance of positive elements for all of America.

The most obvious reason that Reconstruction was a failure can be seen if you just think about the status of African Americans in the years after Reconstruction ended.

One of the major points of Reconstruction was to make blacks equal citizens in the eyes of the law (as the Civil War Amendments made clear).  But this really did not happen.  As soon as Reconstruction ended and the Southern states were allowed to do what they wanted, they imposed segregation on blacks and did all sorts of things to prevent them from voting.

In addition, Reconstruction failed to help blacks economically.  They did not get the "40 acres and a mule" that they hoped for and so they continued to be poor farm workers who pretty much had to work for the rich landowners.  This was not much different from how things had been during slavery.

Reconstruction was the period from 1865 - 1877 where the government of the United States tried to put the country together again after the Civil War.  In general, historians consider it an unsuccessful effort for several reasons.

Politically, the government did convince southern states to rejoin the Union in a fairly simple process.  They also managed to pass the 13th, 14th and 15th amendment.  Past that, not much went well.

The Freedmen's Bureau was underfunded and cut short, leaving the vast majority of free slaves uneducated and still in the South.  There was no land reform, meaning slaves were forced into a sharecropping system and did not own their own farms, which might have made them more independent, equal and successful.

The Black Codes and other laws restricting former slaves, though clearly unconstitutional, were not challenged in court or struck down by local military authorities, leaving African-Americans virtually unprotected and subject once again to working for whites involuntarily.

And finally, the effort of Reconstruction was cut off after only 12 years, leaving the economy of the South still in ruins and its population largely in poverty.

Reconstruction was a failure largely because of division among Republicans about the purpose of reconstruction and a fervent backlash against reconstruction by former Confederates. Lincoln envisioned reconstruction as a means of weakening the power of former Confederates in the southern states while more radical Republicans viewed reconstruction as a means of ensuring more racial equality. This became more complicated after Lincoln was assassinated, as Andrew Johnson opposed more robust reconstruction measures and took a much more lenient attitude toward former Confederates. Johnson's actions allowed for the development of black codes and the suppression of black voices in the public square in southern states, undermining the purposes of reconstruction envisioned both by Lincoln and by more radical Republicans. Johnson's stubbornness ultimately led to the passage of the Civil Rights Act over his veto (and also led to his later impeachment by the House of Representatives).

In response to Johnson's handling of reconstruction, the more radical branch of the Republican party pressed for a more forceful reconstruction effort. This led to violent backlashes in the southern states, including the creation of the Ku Klux Klan. The rash of terrorism perpetrated by the KKK and other groups like it, combined with complaints about governance in southern states (often falsely blamed solely on African American politicians) caused support for reconstruction to ebb until the election of Rutherford Hayes. Disputes over the returns of a few southern states ultimately led to a compromise position in which the representatives of the disputed states agreed to allow congressional certification of Hayes's victory in exchange for the removal of federal troops supporting reconstruction and the acknowledgement of new Democratic governments in those states.

More details can be obtained from the link below, which was written by Eric Foner, one of the foremost experts on the Reconstruction period.

The major reason was a lack of political will to promote equality. While the number of abolitionists grew, it was only a minority of them who sought to give African Americans full civil rights and suffrage. Many, including Lincoln during the latter stages of his presidency, believed that African Americans should be encouraged to expatriate because it would be the only way they could get fair treatment. The South did not appreciate military occupation after the war and they sought legal means to keep African Americans from the ballot box and to preserve the antebellum social status quo by promoting segregation and grandfather clauses to keep African Americans away from equal resources. The Freedman's Bureau suffered as some saw it as too much federal overreach and it eventually expired due to lack of funding from Congress.

Another reason that cannot be ignored is political infighting. The Radical Republicans sought to punish anyone they deemed a "Rebel" even if this meant keeping most white Southerners away from the polls. White Southerners initially voted for their antebellum leaders such as Alexander Stephens as they had the name recognition to win at the polls. Andrew Johnson could not unify the nation and the Radicals saw him as a Democratic traitor. While Reconstruction did eventually unify the nation under the Compromise of 1877, the issue of race relations was still an open question in the South.

I think that one could argue both sides of it quite passionately.  While it might not be a result of the Reconstruction Era, I would say that the passage of Amendments 13, 14 and 15 are extremely meaningful and, by themselves, could constitute Reconstruction as a success in my mind.  The very idea that the Constitution would have a voice about the nature of the Civil War and "speaking" to the end of preventing future conflicts like it would help to solidify its place as a success.  Additionally, the Civil Rights Amendments passed help to move the discussion of race as something viable and a discourse that would grip the nation even to the modern setting.  The fact that the government would be able to establish such elements through the Constitution is something quite impressive.

In addition to what has been mentioned, Reconstruction also failed as what has been known as "carpetbaggers" came down from the North and took advantage of the devastated South both financially and politically Since anyone who had participated in the Confedercy was not allowed to hold public office, the businessmen, lawyers, newspaperment, etc., who came from the North placed men in office who could be manipulated by them.  Many "carpetbaggers" bought farms and mansions for only the back taxes, leaving the original residents homeless.  Exploitation abounded as "confidence men" like those portrayed by Mark Twain with the Duke and the King in "The Adventures of Huckleberry Finn" swindled the unsuspecting in their quest for making a profit from a defeated people.  In short, the South was treated worse than any country that the United States has defeated.

 It took years and years for Atlanta to recover structurally and economically from its burning and total destruction by General Sherman's men.  That the South was exploited by the carpetbaggers is documented by President Grant's ordering them out of the South.  And U.S. history also shows that the South has long been crippled as it has had need of federal aid.  It is only recently with its burgeoning auto industry and other manufacturing that has moved from the North that the South now shows real signs of prosperity.

I very much agree with phonpei397's points but would like to comment on the idea that Reconstruction may be viewed as a success because

it did work.  At the end of Reconstruction, blacks were still free.  And by the end of that time, the Southern states were able to join the Union again.

Blacks were still legally free and equal, yes, but with the end of Reconstruction came a dramatic "rollback" of the important rights that had been extended to blacks, including voting rights and equal access to public facilities. The internet is rich in material covering the Jim Crow laws of the Southern and border states.

In the final analysis, at the risk of sounding too pessimistic, I think that Reconstruction failed to dismantle the racist structures in the South. That dismantling required a second forceful intervention of national government (including not another extended military occupation but certainly including some deployment of national troops) in the late 1950s and early 1960s.

It really depends on how you define success or failure and it depends on how long of a time period you are looking at.

If you just look at the period of Reconstruction and right after it, Reconstruction clearly failed in my opinion.  Here, I am saying it failed because blacks were not equal to whites after Reconstruction (so that's my definition of failure here).  At the end of the period, blacks were still much poorer than whites and they (by late in the 1800s) were not able to vote and were subject to segregation.

Of course, if you define success differently, it did work.  At the end of Reconstruction, blacks were still free.  And by the end of that time, the Southern states were able to join the Union again.  So if that's how you define success, it did succeed.

Some scholars argue that Reconstruction did work, but you have to look longer after Reconstruction to see it.  They say that Reconstruction made black people start working for rights.  They say it succeeded because the black people eventually got all the same rights as whites.  They say that process started back in Reconstruction.

Despite the early successes of the Reconstruction era, the movement should be considered a failure. The goals of Reconstruction were to rebuild the economy of the South while successfully integrating the newly freed slaves into the culture and marketplace of the United States. The effort failed on both parts. The gap in wealth between the North and South had widened even more by the turn of the Twentieth Century. Additionally, African-Americans were only slightly better off than before the Civil War.

Despite the best efforts of the Radical Republicans in Congress to protect the rights of the Freedman, Southern Democrats opposed any social change for the black people of the South. By the end of Reconstruction, the 13th, 14th, and 15th Amendments were not worth the paper they were written on. Black codes were established to deny basic civil liberties to the freedmen. A system of sharecropping and tenant farming kept the African-Americans on the plantations with little hope for upward social mobility. Schools and other social institutions were segregated. Due to poll taxes and terrorist organizations like the Ku Klux Klan, black people could not even secure the most basic of democratic rights: the ability to vote. Black Americans, while making significant political strides in the early 1870's, had lost everything with the Compromise of 1877.

One of the more disturbing observations that one can make about United States history with respect to the outcomes of the Civil War and the period of Reconstruction was the fact that institutionalized racial segregation and the struggle among African Americans for civil rights survived more than halfway into the 20th century. Legislation granting basic rights to African Americans was still being debated in the United States Congress a century after the end of the Civil War. That is a failure of Reconstruction.

Reconstruction was a process whereby the South, physically and mentally defeated, would essentially be rebuilt physically and politically to better mirror the North. It was a process of reuniting two very disparate entities. The war cemented the South’s unification with the North. Reconstruction was needed to maintain that unity by culturally and politically transforming the vestiges of the South—an effort that could be termed, to employ a World War II vernacular, as "a bridge too far." Reconstruction succeeded insofar as the adoption of state constitutions and legislatures more in-tune with the post-war mandate at eliminating slavery and incorporating newly-freed slaves into the nation’s fiber was achieved. Politically, in other words, Reconstruction could be viewed as a success. It was, in the broader sense, however, a failure in that the cultural transformations required to bring the South into alignment with the North did not occur. In fact, the notion of “carpetbagging” was born to symbolize a sense among Southerners of Northern imperialism being imposed upon a proud culture, however morally defective that culture remained regarding racial equality.

Because the South continued to resist, often militaristically in the form of white supremacist terrorists like the Ku Klux Klan, and politically in the form of Jim Crow laws, the advance of the United States as a nation more representative of the ideals upon which it was founded would be delayed for many tumultuous decades. That was a failure of Reconstruction.

There were stunning social and economic successes and failures as well.  Socially, Reconstruction successfully put blacks on equal legal footing with whites, but did not change southern (or national) racist sentiment.  Slavery had ended, but it was replaced with something else.

Most importantly, Reconstruction began a social change by starting schools for freed slaves, and basic literacy for nearly 200,000 former slaves was achieved in only six years.  But that funding was cut in 1871, and the remaining 3.8 million freedmen were still uneducated.

Economically, limited land reform ideas had been pursued, most notably in the South Carolina Sea Islands and the Davis Bend Plantation, where former slaves received their own land to farm, and did amazingly well, forming co-ops and sharing costs and labor.  But no widespread land reform happened, and another golden opportunity was missed.