The Public Land Survey System (PLSS) is a rectangular survey system.  It is called a rectangular system because wherever practicable the units are in rectangular form.  The rectangular survey system divides land into townships and ranges. A regular township is six miles on a side bounded on the North and South by township lines, and the East and West by range lines.  The township is divided into thirty-six sections, each one mile on a side, comprising about 640 acres, which was the basic unit under the Land Ordinance Act of 1785.  No township or section is mathematically perfect for various reasons, including the fact that the earth's surface is not flat.
 

The Geographic Coordinate Data Base (GCDB) is the digital coordinate-based representation of the Public Land Survey.  The GCDB is where GIS and the Public Land Survey meet. For more on the GCDB, see Part Three.

Use the links below to learn more about the PLSS.

PLSS Datum
Metes And Bounds Surveys, and Lots
Legal Description
Plats
Geodetic Control