Section (United States land surveying)

In U.S. land surveying under the Public Land Survey System (PLSS), a section is an area nominally one square mile (2.6 square kilometers), containing 640 acres (260 hectares), with 36 sections making up one survey township on a rectangular grid.

The legal description of a tract of land under the PLSS includes the name of the state, name of the county, township number, range number, section number, and portion of a section. Sections are customarily surveyed into smaller squares by repeated halving and quartering. A quarter section is 160 acres (65 ha) and a "quarter-quarter section" is 40 acres (16 ha). In 1832 the smallest area of land that could be acquired was reduced to the 40-acre (16 ha) quarter-quarter section, and this size parcel became entrenched in American mythology. After the Civil War, freedmen (freed slaves) were reckoned to be self-sufficient with "40 acres and a mule," though they never received it. In the 20th century real estate developers preferred working with 40-acre (16 ha) parcels. The phrases "front 40" and "back 40," referring to farm fields, indicate the front and back quarter-quarter sections of land.

One of the reasons for creating sections of 640 acres (260 ha) was the ease of dividing into halves and quarters while still maintaining a whole number of acres. A section can be halved seven times in this way, down to a 5-acre (2 ha) parcel, or half of a quarter-quarter-quarter section—an easily surveyed 50-square-chain (2 ha) area. This system was of great practical value on the American frontier, where surveyors often had a shaky grasp of mathematics and were required to work quickly.

A description of a quarter-quarter section in standard abbreviated form, might look like "NW 1/4, NE 1/4, Sec. 34, T.3S, R.1W, 1st P.M." or, alternatively, "34-3-1 NW4NE4 1PM". In expanded form, this would read:

The Northwest quarter of the Northeast quarter of Section 34 of Township 3 South, Range 1 West, first Principal Meridian.

The existence of section lines made property descriptions far more straightforward than the old metes and bounds system. The establishment of standard east-west and north-south lines ("township" and "range lines") meant that deeds could be written without regard to temporary terrain features such as trees, piles of rocks, fences, and the like, and be worded in the style such as "Lying and being in Township 4 North; Range 7 West; and being the northwest quadrant of the southwest quadrant of said section," an exact description in this case of 40 acres, as there are 640 acres (260 ha) in a square mile.

The importance of "sections" was greatly enhanced by the passage of "An Ordinance for ascertaining the mode of disposing of lands in the Western Territory" of 1785 by the U.S. Congress (see Land Ordinance of 1785). This law provided that lands outside the then-existing states could not be sold, otherwise distributed, or opened for settlement prior to being surveyed. The standard way of doing this was to divide the land into sections. An area of six sections by six sections would define a township. Within this area, one section (section 16) was designated as school land. As the entire parcel would not be necessary for the school and its grounds, the balance of it was to be sold, with the monies to go into the construction and upkeep of the school. Section 36 was also subsequently added as a school section in western states. The ordinance also specified that out of every township, the four lots, being numbered 8, 11, 26, 29, and out of every fractional part of a township, so many lots of the same numbers as shall be found thereon, for future sale.

On May 20, 1862, President Abraham Lincoln signed into law the Homestead Act, by which settlers could "claim" 160 acres (a quarter section) of public land. Claimants were required to "live on" and “improve” their plots by cultivating the land. After five years, the original filer of the claim was entitled to the property, free and clear, except for a small registration fee.