Or even sooner. Money is the story of wealth, but the real working and growing economy was almost always about debt. The moment someone invented writing someone wrote a letter of credit. Kings used it, and countries got built on next year's harvests, and of course went bankrupt when that harvest turned out bad.

It was in 1971 that US got off the gold standard, but yea even in the 1960s there was signs of trouble I think.