east-west lines in the government rectangular survey system are known as
Public Land Survey System The surveying of any regional area, such as a state or two, is a multi-step process. First, two controlling survey lines are established: a baseline, which runs east-west and a principal meridian, which runs north-south (Fig. 1). The locations of the two are determined by a previously chosen initial point, where they originate and thus intersect. Next, at a defined distance interval, commonly 24 or 30 miles (48 km) depending on the year and location, standard parallels of latitude are established parallel to the baseline. The meridian, baseline and standard parallels thus established form a lattice upon which all further surveying is then based. Subsequent work divides the land into survey townships of roughly 36 square miles (~93 km2) or 6 miles (~9.7 km) on each side. This is done by the establishment of township and range lines. Township lines run parallel to the baseline (east-west), while range lines are true meridians and thus run north-south; each are established at six mile (10 km) intervals. Lastly, townships are subdivided into 36 sections of approximately one square mile (640 acres, ~2.6 km2) and sections into four quarter-sections of 0.25 square mile (160 acres, ~0.65 km2) each. (See descriptions and figures illustrating the system). The intersection of a township line (or baseline) with a range line (or principal meridian) constitutes a township corner, of a section line with any other type of line a section corner, and a point halfway between any two section corners a quarter corner. The federal government typically surveyed only to this quarter-section level, the subdivision of smaller parcels being carried out subsequently by private surveyors after original sale.