A multi-wire proportional counter (MWPC) was designed and successfully tested along the focal plane of the Rice University 65 cm magnetic spectrograph. The MWPC, which utilized .002" diameter stainless steel wires, a .100" wire spacing, and a .250" gap length, had an active area of 1" x 12". Counter efficiency and spatial resolution were determined by comparing the MWPC to results obtained with a position-sensitive solid state detector. The MWPC was thus found to be at least 98% efficient in the detection of 6 MeV protons. The spatial resolution of about 3 mm was limited by the multiple scattering of the protons in the counter foils and gas.