Dang, what DID happen during the reconstruction then? It's way more fun to have you say it rather than books or google
So 1865-1876 is one of the most important decades in American history like genuinely our failure to do this right is the root of all evil today. It is very complicated. Here is the best shortest answer i can give you.
After the Civil War, with the plantation south destroyed and about 5 million previously enslaved people freed, the American government faced two big questions: what to do to reconcile the South back into the union to prevent another civil war, and what the social, economic, and political status of freedpeople in the South was going to be. Note that at this time Republicans were liberal and Democrats were conservative.
Abraham Lincoln had a plan that was a bit too lenient to the South than his more radical party members in Congress liked, but he was more committed to Black civil rights than his Democratic contemporaries. Radical Republicans wanted to take steps to ensure none of this would happen again, including redistributing land to freedpeople as a form of reparations, mass industrialization in the South, and preventing white ex confederates from voting or holding office while giving freedpeople the right to vote. Southern Democrats (white supremacists. Not that northerners werent but christ alive these were evil people) resisted this at all costs.
Unfortunately for everyone to this day, Lincoln’s vice president was a southern democrat, so when Lincoln got shot in the hat and died, now-president Andrew Johnson decided to let mostly everything slide. He let the Southern states back in with very few guardrails, took redistributed land and gave it back to enslavers (they had to personally ask him because he liked when they begged), and generally neglected Black civil rights the entire time he was President because he was super racist. Congress (much more radical) ended up in the drivers seat of Reconstruction halfway through his admin.
Congress passed the 13th Amendment to end slavery except as a punishment for a crime. White ex-confederates retaliated by passing the Black Codes, state laws that made it a crime to exercise really any social or economic autonomy while Black so that freedpeople could be incarcerated or coerced into essentially doing the same plantation labor they previously had been. Many white plantation owners put Black people (later also poor whites) into perpetual debt with systems like sharecropping and crop-lien, so they could not afford their own land. A lot of it was recreating the conditions of slavery in the aggregate using capitalism and a white supremacist legal system.
The federal government passed the 14th and 15th Amendments, which nullified the Black Codes, protected Black citizenship, disenfranchised white ex-confederates for a while, and protected the right of Black men to vote. This was especially critical in states like South Carolina and Mississippi, which had Black majorities. Some Southern states had biracial (black and white) populist political parties, because poor whites had common class interests with many freedmen.
White ex-confederates responded to these civil rights milestones with what can only be described as mass terrorism: the formation of the KKK, sundown towns, widespread lynchings, voter intimidation, voter fraud, public beatings, etc. President Grant, who took office after Johnson, tried to combat this by putting chunks of the South under martial law, which sort of worked when the army was in fact there.
However, Grant was mired in scandal and not super popular, and it really came to a head during the panic of 1873: the economy got bad, and lots of white northern liberals lost enthusiasm to keep forcing the white south into modernity. They decided essentially that they had their own problems to deal with, that Black people could fend for themselves, and that white ex-confederates had “been through enough” (very little.) White Southern racists called “redeemers” gained a lot of political power during the mid 1870s as more white people got their right to vote back.
All of this comes to an end in the election of 1876: due to “voting irregularities” in SC, LA, and FL (an overt violent white supremacist coup in SC and some significant fraud in the latter states), the election came down to the House of Representatives instead of the Electoral College. Rutherford B Hayes, the Republican candidate, promised the white south that if they made him the president, he would pull all the US troops protecting civil rights and fighting the Klan out of the South and end reconstruction. They happily took that deal, actively condemning millions of African-Americans to a century of severe white supremacy.
After reconstruction, the white South passed Jim Crow laws like segregation and voter disenfranchisement to cement the electoral, social, and economic control of southern whites. The US Supreme Court also enforced these (racism is a national problem.) The biracial political coalitions of Reconstruction died out as more and more poor whites picked white supremacy over class solidarity.
Conditions for African-Americans obviously improved over literal slavery, but the South remained a deeply racist, largely agrarian, and economically regressive place for a long time. Many opted to flee the South for the urban north in the early 1900s. A lot of the damage done by the failure of Reconstruction did not get addressed until the Civil Rights movement, and a lot of it still hasn’t been addressed at all.
Watch this video it will help you with the basics.