We present observations of 1116 current sheet crossings in the Martian magnetotail during one Martian year, as identified from magnetic field rotations measured by Mars Global Surveyor (MGS) at ~400 km altitude and 2 am local time. Crossings are observed everywhere except above strong crustal fields, and many occur in clusters, with preferred locations varying as a function of season and IMF draping direction. Magnetic polarities are consistent with day-side IMF draping directions and a two-lobe induced magnetotail. Energetic "plasma sheet" electrons are often absent, implying that currents can be carried by ions or low-energy electrons, with thicknesses of <~100 km arguing for electrons. The presence of a thin current sheet at low altitudes, with specific seasons and IMF directions favored for some geographic locations, implies that reconnection between crustal fields and the draped IMF may play an important role in its formation and location.