Nations attempted to revive the gold standard following World War I, but it collapsed entirely during the Great Depression of the 1930s. Some economists said adherence to the gold standard had prevented monetary authorities from expanding the money supply rapidly enough to revive economic activity. In any event, representatives of most of the world's leading nations met at Bretton Woods, New Hampshire, in 1944 to create a new international monetary system. Because the United States at the time accounted for over half of the world's manufacturing capacity and held most of the world's gold, the leaders decided to tie world currencies to the dollar, which, in turn, they agreed should be convertible into gold at $35 per ounce.

Source:
http://economics.about.com/od/foreigntrade/a/bretton_woods.htm