PLSS

The Public Land Survey System (PLSS) is the rectangular survey system used to divide and describe the public lands of the United States. Land in the system is identified by principal meridian, township, range, section, and the parts of a section.

BLM's Manual of Surveying Instructions (2009) says the rectangular system "provides a simple and certain form of land identification and legal description" and "has been used continuously since 1785" (section 3-1).

Where it came from

BLM's Specifications for Descriptions of Land (2017) traces the system to the Land Ordinance passed by the Congress of the Confederation on May 20, 1785. Ohio served as the proving ground. The Manual notes that the PLSS, based on field surveys that set monuments before conveyance, replaced the Colonial practice of describing land by irregular metes and bounds (section 1-18).

How the grid is built

The Manual lists the steps in order (section 3-3):

1. Initial points, each the origin for surveys in a region
2. Principal meridians and base lines, run from the initial points
3. Guide meridians and standard parallels, to keep each township close to "6 miles square"
4. Township exteriors, numbered north or south from the base line and east or west from the principal meridian
5. Subdivision of each township into 36 sections, numbered from 1 in the northeast to 36 in the southeast

Under the general scheme, "the unit of survey is the township of 36 sections" and "the unit of subdivision is the section of 640 acres" (section 3-2). Federal law requires the lines to be run "according to the true meridian" (43 U.S.C. 751).

Where it applies

The Specifications list 30 public land states that made up the original public domain, including every western mining state: Alaska, Arizona, California, Colorado, Idaho, Montana, Nevada, New Mexico, Oregon, Utah, Washington, and Wyoming. For land not yet surveyed on the ground, the Manual says protraction diagrams "have been prepared for substantially all unsurveyed areas in the public domain" (section 3-12).

The PLSS and the mining laws

Federal law directs that the "public surveys shall extend over all mineral lands" (43 U.S.C. 766, quoted in Manual section 1-20). The Mining Law ties placer mining claims to the grid: they "shall conform as near as practicable with the United States system of public-land surveys, and the rectangular subdivision of such surveys" (30 U.S.C. 35, quoted in section 10-108). Lode mining claims are different. The Manual records that under the 1872 Mining Law, lode mining claims and tunnel sites were described by metes and bounds, while placer mining claims and millsites were described by the rectangular system (section 1-13(n)).

Why it matters in research

In mining claim research the PLSS is the index. BLM's MLRS records, master title plats, and county filings are organized by meridian, township, range, and section. A description that leaves out the meridian points to no ground at all.