1929-1948 gave investors a +0.6%/year, which I think is the lowest nominal return. 1962-1981 was +0.8%/year.

As you allude, there were 20-year periods spanning the 1970s where Treasuries outperformed large-caps, but that’s fairly rare (and with the printing presses running three shifts, something we’re in extremely little danger of right now).