PLSS Map

http://www.nationalatlas.gov/articles/boundaries/a_plss.html

The Public Land Survey System (PLSS) is a way of subdividing and describing land in the United States. All lands in the public domain are subject to subdivision by this rectangular system of surveys which is regulated by the U.S. Department of the Interior. Each PLSS consists of a series of separate surveys. Most surveys begin at an initial point, and townships are surveyed north, south, east, and west from that point. The north-south line runs through the initial point and is called the Principal (true) Meridian. There are also 37 Principal Meridians and each is named to distinguish various surveys. The east-west line runs through the initial point and is called a base line; line is perpendicular to the Principal Meridian.