Happy Birthday to You, which she wrote with her sister, Patty S. Hill, was intended as a classroom greeting. It was first published in 1893 as "Good Morning To All." The lyrics were amended in 1924 to include a stanza beginning "Happy Birthday to You.".
In 1988, Birch Tree Group, Ltd. sold the rights of Happy Birthday to You, along with all its other assets, to Warner Communications for an estimated $25 million. With Auld Lang Syne and For He's a Jolly Good Fellow, Happy Birthday to You is among the three most popular songs in the English language. The song is expected to enter public domain upon expiration of copyright in 2030.
Mildred J. Hill and Patty Smith Hill are postumously inducted into The Songwriter's Hall of Fame. [June 1996]
She and sister, Patty Smith Hill, are buried at Cave Hill Cemetery (Louisville, KY)