From USGS:The Public Land Survey System (PLSS) is a way of subdividing and describing land in the United States. PLSS surveys, which are available for portions of land in 30 southern and western states, are made by the Bureau of Land Management (BLM). The PLSS typically divides land into 6-mile-square townships. Townships are subdivided into 36 one-mile-square sections. Sections can be further subdivided into quarter sections, quarter-quarter sections, or irregular government lots. PLSS was created to divide parcels of public land; it is not useful for the accurate location of points and should not be confused with coordinate systems like latitude/longitude, UTM, or the State Plane Coordinate System.