These stamps were issued to commemorate the 25th anniversary of the signing of the United Nations Charter. Delegates from 50 nations met in San Francisco in April 1945 for the United Nations Conference on International Organization. After much discussion, on June 26, 1945, all 50 nations present voted to accept the Charter. The Charter then had to be approved by the governments of a majority of the nations that signed it. It went into effect on October 24, 1945, a date celebrated each year as United Nations Day.