Initial Point, PLSS Definition

Every PLSS survey area begins at a single, precisely monumented geographic point called the initial point. This is the location where the principal meridian — the north-south reference line — crosses its associated baseline — the east-west reference line. All township and range numbering within that survey area radiates outward from this point.

Initial points were established by federal surveyors with great care. The location was chosen for its geographic stability, accessibility, and ability to be precisely described. The point was marked with a permanent monument — initially a wooden post or stone, later a brass cap set in concrete. The coordinates of initial points were determined astronomically before GPS was available, making them among the most precisely located points in the historical survey record.

There are 37 initial points in the continental United States, each associated with a named principal meridian. The Willamette Meridian's initial point, for example, is located in the Tualatin Mountains southwest of Portland, Oregon. The Black Hills Meridian's initial point is in South Dakota. The Sixth Principal Meridian's initial point is in Kansas. Some initial points are now on private land; others are in parks or other public areas and are marked with interpretive signs.

When converting a legal land description to GPS coordinates, the software calculates the location by starting at the initial point and mathematically stepping through the township, range, section, and aliquot part designations. The accuracy of the conversion depends on how precisely the initial point's coordinates are known and how closely the actual survey followed the theoretical grid. Because surveys were conducted over many decades by different survey parties, there can be small inconsistencies that only cadastral survey data can resolve.