Bretton Woods - A Brief History of the World Reserve Currency

In World War II, the allies had shipped all their gold to the US treasury and the New York Fed. By the end of the war, the Fed held over 50% of the above ground gold in the world. And so they were able to dictate the terms of the post-war economic quarter. The dollar was pegged to gold at $35 an ounce; other nations would peg their currencies indirectly or directly to the dollar.