As Timely segued into Atlas Comics, Marvel's 1950s predecessor, Hartley made his mark with a more than decade-long run on the "Patsy Walker" teen-girl titles. With writer-editor Lee, Hartley chronicled the redheaded high schooler's lightly comic adventures in her namesake series (which ran through 1964) and in its spin-offs, "Patsy and Hedy" (which ran through 1967) and the single-issue "A Date with Patsy" (Sept. 1957). Well into the Marvel era, Hartley also drew the "Special Queen Size Annual" publication "Patsy Walker's Fashion Parade" #1 (1966). Walker eventually would be integrated into mainstream Marvel Universe continuity in the 1970s as the supernatural superheroine Hellcat long after Hartley had left the character.