The left side of Greg Iron's guitar was a mirror image of the right and advertised a double-Blues billing: Butterfield Blues and Mike Bloomfield.
Irons moved to San Francisco in 1967 and roamed around Haight-Ashbury with his sketchbook, creating images he would later use in his posters. As usual, promoter Bill Graham needed a poster in a hurry, and Irons succeeded in producing one overnight. As his talent as a draftsman developed, a distinctive line quality and refined sense of balance set Irons' posters apart. His cartoonist inclinations are often evident, and he became one of the seminal figures in underground comics. Irons also found work producing album graphics and book illustration, but it was the art of tattooing that became his passion.