On the recordApril 25, 1951
I, Harry S. Truman, President of the United States of America, do hereby direct the appropriate officials of the Government to arrange for the display of the flag of the United States on all public buildings on Mother's Day, May 13, 1951, and I call upon the people to display the flag on that day at their homes or other suitable places as a public expression of honor for our mothers.
Source
presidency.ucsb.edu
