Survey township

Survey township, sometimes called Congressional township, as used by the United States Public Land Survey System, refers to a square unit of land, that is nominally six (U.S. Survey) miles (~9.7 km) on a side. Each 36 square mile (~93 km²) township is divided into 36 one-square mile (~2.6 km²)  sections, that can be further subdivided for sale, and each section covers exactly 640 acres. To be more precise, the subdivisions of a section are frequently the quarter-section (160 acres) and the quarter-quarter section (40 acres). In the Homestead Act of 1862, one quarter-section of land was the amount allocated to each settler. Stemming from this is the expression, "the lower 40", which is the 40 acres on a settler's land that is lowest in elevation, in the direction towards which water drains toward a stream, and the "back forty", the portion farthest from the settler's dwelling. The townships are referenced by a numbering system that locates the township in relation to a meridian (north-south) and a base line (east-west).
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