The equivalent circuit concept derives from the Superposition Principle and Ohm's Law. Two forms of the equivalent circuit, the Thevenin equivalent and the Norton equivalent, distill any linear circuit into a source and an impedance. The development of these equivalents spans almost seventy-five years, with others than the eponymous people assuming equally important roles. This report describes the pertinent biographies of Mayer and Norton, and provides the relevant sections from their original papers on equivalent circuits.