Different hemoglobins, as distinguished by electrophoretic mobility, are alphabetically designated in order of discovery (eg, A, B, C), although the first abnormal hemoglobin to be identified, sickle cell hemoglobin, was designated hemoglobin S Structurally different hemoglobins with the same electrophoretic mobility are named for the city or location in which they were discovered (eg, Hb S Memphis, Hb C Harlem).