For most of this country's history, the dollar was exchangeable into gold or silver. "Sound" money was the kind that rang when you dropped it on a counter. For a long time, the rate of exchange was an ounce of gold for $20.67. Following the Roosevelt devaluation of 1933, the rate of exchange became an ounce of gold for $35. After 1933, only foreign governments and central banks were privileged to swap unwanted paper for gold, and most of these official institutions refrained from asking (after 1946, it seemed inadvisable to antagonize the very superpower that was standing between them and the Soviet Union). By the late 1960s, however, some of these overseas dollar holders, notably France, began to clamor for gold. They were well-advised to do so, dollars being in demonstrable surplus. President Richard Nixon solved that problem in August 1971 by suspending convertibility altogether. From that day to this, in the words of John Exter, Citibanker and monetary critic, a Federal Reserve "note" has been an "IOU nothing."  The entire opinion here.