The “Happy Birthday” song originated in Louisville in the late 19th century. Patty Hill, a teacher at the Louisville Experimental Kindergarten School, collaborated with her sister Mildred, a piano instructor, on a song called “Good Morning to All” that became a greeting teachers would sing to students. It’s unclear how, exactly, the tune morphed into “Happy Birthday to You,” but today it’s the most recognizable song in the English language.