Diamond was a "young, broke songwriter" when a photo of the president's daughter in a news magazine caught his eye.
"It was a picture of a little girl dressed to the nines in her riding gear, next to her pony," Diamond recalled. "It was such an innocent, wonderful picture, I immediately felt there was a song in there."
Years later, holed up in a hotel in Memphis, he would write the words and music in less an hour.
"It was a No. 1 record and probably is the biggest, most important song of my career, and I have to thank her for the inspiration," he said. "I'm happy to have gotten it off my chest and to have expressed it to Caroline. I thought she might be embarrassed, but she seemed to be struck by it and really, really happy."