Harry Truman actually said...
Now, Therefore, I, Harry S. Truman, President of the United States of America, do hereby ask that on Flag Day, June 14, 1949, the people of the Nation honor our colors by displaying them at their homes or other suitable places and by giving thanks for their privileges as citizens under this flag as well as by engaging in earnest contemplation of the obligations inherent in citizenship.
05/23/1949