Where is the poem "Footprints in the Sand" from?

Mary Stevenson wrote the poem "Footprints in the Sand" in 1936 as a young girl, but she was not aware of copyright laws at the time. Subsequent copies were signed "Author Anonymous," but many authors claimed authorship.

In 1984, while preparing for a household move, Stevenson discovered a handwritten copy dated 1939 that she had thought was lost. The U.S. Copyright Office awarded Stevenson a copyright that same year, and a forensic specialist verified the poem's authenticity in 1959. Originally, Stevenson distributed handwritten copies of the poem to her friends who were experiencing hard times in the hopes that it would provide some comfort, according to her estate website.