Here are key dates in gold's trading history since the early 1970s:
August 1971 - U.S. President Richard Nixon takes the dollar off the gold standard, which had been in place with minor modifications since the Bretton Woods Agreement of 1944 fixed the conversion rate for one troy ounce of gold at $35.
August 1972 - The United States devalues the dollar to $38 per ounce of gold.
March 1973 - Most major countries adopt the floating exchange rate system.
May 1973 - U.S. devalues dollar to $42.22 per ounce.
For inflation adjusted gold price timeline, see here