Irving Chernev and Fred Reinfeld, in the Fireside Book of Chess, state that this list was devised by H. Threkeld-Edwards, a surgeon, and Prof. Mansfield Merriman, teacher of civil engineering at Lehigh University, Bethlehem, PA, who challenged Pillsbury in Philadelphia, PA, before an exhibition in 1896. (Other sources cite the location of the challenge as London, UK.)