Founding of the country and the civil war? Considering the primitive weapons systems employed at those times, I doubt the debts incurred were anything to worry too terribly about. More importantly, there was no reason to believe that economic growth would falter.
As for WWII, see the chart below. Note that the falloff in GDP in the early thirties is what drove the ratio higher during that period. When GDP hits the skids this time, I expect a percentage greater than 500%.
Still here and prosperous? For the moment, yes.
From 1971, direct from the Fed itself: