Robert Indiana kept a series of illustrated journals during the late 1950s and 1960s, in which he discusses the development of his work.

His journal page for February 1, 1961, is dominated by a color sketch of the painting The American Sweetheart, with a note to the left indicating to add names to the twenty circles in the work. Below the sketch, Indiana records that he had a visit from St & Barb (Stephen and Barbara Durkee), and that their reaction to his works The American Sweetheart and The Sweet Mystery was positive.