Principal Meridian
A north-south reference line running through an initial point, from which ranges are numbered east and west.
Detailed Definition
A principal meridian is a true north-south line extending from an initial point, serving as the primary reference for measuring ranges in the Public Land Survey System (PLSS).
Characteristics: - Runs due north and south (true meridian) - Passes through the initial point - Serves as the zero line for range numbering - Named for geographic features or historical figures
Function in PLSS: - Ranges are numbered east and west from the principal meridian - Example: R5E means Range 5 East of the principal meridian - Combined with township numbers to locate land - Forms the vertical axis of the survey grid
Principal meridians in the U.S.: There are 37 principal meridians, including: - 6th Principal Meridian (Kansas, Nebraska, Colorado, Wyoming) - Boise Meridian (Idaho) - Mount Diablo Meridian (California, Nevada) - New Mexico Principal Meridian - Willamette Meridian (Oregon, Washington)
Legal descriptions: Mining claims and land descriptions must specify which principal meridian applies (e.g., "T3N, R5W, Boise Meridian").
Related Terms
PLSS
The Public Land Survey System, a method of subdividing and describing land in the United States using townships, ranges, and sections.
Township, Range, and Section
The hierarchical land description system within PLSS, identifying land by its position relative to principal meridians and base lines.
Initial Point
The geographic starting point from which all PLSS surveys in a given region originate, established by astronomical observation.
Base Line
An east-west reference line running through an initial point, from which townships are numbered north and south.