The Public Land Survey System publishes grid-like maps that break public lands down into 6-mile squares called townships, then subdivides each township into 36 1-mile squares called sections. Heavily populated sections are further divided into quarter-sections or quarter-quarter-sections. The PLSS assigns each township a township designation to show how far north or south of a baseline it lies, and a range designation to show how far east or west it lies from a principal meridian.
The PLSS was established to map and manage all of the lands owned by the federal government. It includes major portions of the land in 30 Midwest, Western and Southern states. There are 37 principal meridians with perpendicular baselines that intersect at the initial points of the original land surveys. The disparate surveys were combined into a single system that is now used in the legal description of each property within the survey area.
During the survey process, monuments or markers were placed at each section corner. Early markers were fashioned from readily available materials, such as wooden stakes, marked trees or piles of rocks. Modern markers are more permanent, such as inscribed concrete slabs or iron rods. Monuments were often erected at important points, such as the corners of government lots and quarter-sections. Although there are irregularities in the measurements of some sections, due to variations in technique, errors or fraud, all current surveys must adhere to the original section markers.