The Civil War ended in 1865.
en.wikipedia.org
It was funded, owned, created, and commemorated by members of the KKK. It's about as or even more synonymous with the KKK as it is with the figures on the wall. It was the site of their rallies for 50 years until Georgia put a stop to it. Notably the brothers who commenced it did so more to honor the heros of the KKK and mark the land for its purpose, which was cross-burnings and rallies, than the civil war which ended when even the oldest of the 2 brothers was a child.
Sometimes things take on new meanings as they age, but the original meaning is still important too. Many of these statues were put up in the 20th century (like Stone mountain), not the 19th, as a part of Jim Crow laws to oppress black people who were no longer slaves and cement in their descendants who had never been slaves that they still weren't equal.
en.wikipedia.org
"There is a consensus among Egyptologists that the
Great Pyramids were not built by slaves. Rather, it was peasants who built the pyramids during flooding, when they could not work in their lands."