That is strong evidence post WW2 is a competing nomination. At 2.2 vs 2.5 it is probably down into the noise if they are estimates, especially ones from 1800s. This why I did not provide any quantitative comparison.
Down into the noise on a winner, I think I'll take the one with much lower taxes and far lower incarceration rate as my preferred template to break the tie.
There is no reason to believe that they would have achieved the same growth rate had they started with a larger economy.
As I stated, it is much easier to double growth when you're small and ultimately, growth rate doesn't matter as you can't spend growth rates. Nominal growth matters. The economy increasing by $5.5k per capita (2011 $) in the period after the civil war is a lot less impressive than increasing by $23k after WW2.
Down into the noise on a winner, I think I'll take the one with much lower taxes and far lower incarceration rate as my preferred template to break the tie.