To each of us who has enjoyed a piece of birthday cake, the strains of “Happy Birthday to You” are as familiar to our ears as our own names. Yet how many people know the origin of the tune and its place in American history?In 1889 Patty and Mildred Hill, two Kentucky sisters, wrote the words and composed the melody of “Good Morning to All” for their kindergarten students. Initially written as a simple greeting and welcome, they later changed the words and birthday celebrations were forever altered. But it wasn’t until 1935 that the sisters’ song was fully copyrighted and their names duly credited.Margot Theis Raven, the author of such inspiring children’s books as Mercedes and the Chocolate Pilot and Let Them Play, relates the story behind one of the most famous and oft-sung songs in the world.