[jmyeet]

In 1800, the US was an agrarian backwater. By 1900 the US was an industrial superpower. Industrialization predominantly happened in the North. So you could argue that slavery was an impediment to growth but that ignores what happened in between and the secondary effects.

Specifically, the US built a massive cotton industry [1] that created an enormous amount of wealth and funded expansion of hte United States westward. Cheap labor was essential to that. Even partial mechanization (ie the cotton gin) actually just increased demand for slave labor because cotton became much cheaper as a result.

As for prison labor, the direct economic output of incarcerated persons is relatively small to overall GDP but, just like with slavery, you can't ignore the secondary effects, specifically in suppressing in wages.

[1]: https://www.theatlantic.com/business/archive/2014/12/empire-...