Wishing a wonderful day to all of those who may be called Mother!
In the U.S., Mother's Day became an official holiday in 1914. On May 2, 1934, the U.S. issued the Mothers of America issue to commemorate the special day. Below is the perf. 11 flat plate printing of the stamp (Scott 738) featuring an adaptation of Whistler's portrait of his Mother.
The original design for the stamp, sketched out by President Franklin D. Roosevelt, may be viewed on the Postal Museum's website.