The biggest boom and gains in the US arguably happened after the Civil War and before WW1, during which federal tax burden was something like 2% and there was no income tax.
Not on a per-capita basis. Real GDP growth per-capita rose 2.2x* between 1866-1913. That's smaller than say, the period starting after WW2, 1946-1993 which as 2.5x.
Even post-WW1 1919-1966, it went up by roughly the same as post-civil war, 2.2x - and that period includes a depression and heavy income taxes.
Given how much easier it is to double a small economy than a large one, the fact post-WW2 period beat it is doubly impressive.
Also one should note there was actually an income tax from 1861-1872.
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.
There was no FDA to protect the health and well-being of US citizens. FDA helped prevent thalidomide coming to market, unlike Europe at the time. Think of all the snake-oil and harmful drugs that where pushed in the time period you are prescribing.
[0]
That is also the time period of the Labor wars. Those with money and power were miss-treating the average worker. Again goes against the health, well-being, and wealth of the US citizens.
[1]