"Happy Birthday to You" was written by Mildred Hill, an American, in the 1890's. Her sister Patti, a teacher, thought of the lyric "Good morning dear teacher, good morning to you" to fit the melody. Over the years, "Good morning dear teacher, good morning to you" grew in popularity, and was eventually sung in schools across the U.S. Forty years later, Patti came up with the words "Happy Birthday to You, Happy Birthday to You, Happy Birthday Dear (name), Happy Birthday to You," and fit those words to her sister's melody. The entire song was then published in 1935.

The Happy Birthday Song’s popularity really soared in the 1930's when it was sung in the Broadway production of "As Thousands Cheer," and has since become the mega-classic hit of all time. Interestingly enough, the Happy Birthday Song (lyrics and melody together) are still under copyright protection, so every time you hear it sung on TV or radio, for example, royalties are being paid to the publisher, Warner Chapel, in the U.S.