Initial Point
The point where a principal meridian and its base line cross, serving as the origin for Public Land Survey System townships and ranges in a region.
Detailed Definition
An initial point is the origin of a Public Land Survey System (PLSS) region. The principal meridian runs north and south from it, the base line runs east and west, and every township in that region is numbered from it.
BLM's Glossary of Surveying and Mapping Terms defines an initial point as "a point which is established under the rectangular system of surveys and from which is initiated the cadastral survey of the principal meridian and base line that controls the cadastral survey of the public lands within a given area."
How the survey grows from it
BLM's Manual of Surveying Instructions (2009) lists the first steps of the rectangular system in order (section 3-3):
- "The establishment of independent initial points, each to serve as an origin for surveys to be extended in separated localities"
- "The survey of principal meridians and base lines, originating at the initial points"
- Guide meridians and standard parallels, run at intervals short enough to keep townships close to six miles square
Initial points in the West
Each initial point belongs to one meridian. BLM's table of meridians gives the year each was adopted. Examples:
- Mount Diablo (California and Nevada): 1851
- Willamette (Oregon and Washington): 1851
- Salt Lake (Utah): 1855
- Gila and Salt River (Arizona): 1865
- Boise (Idaho): 1867
- Seward (Alaska): 1911
The Manual also notes that "many of the initial points were fixed in position by surveys that were largely completed before importance was attached to the matter of accurate coordinates." What controls is the survey on the ground, not a modern coordinate.
The BLM glossary defines an initial monument as "a physical structure which marks the location of an initial point."
Surveys with no initial point
Not every public land survey has one. BLM notes: "There are eight public-land surveys, seven in Ohio and one in Indiana, which have no initial point as origin for township and range numbers."
Why it matters in research
The initial point decides which township grid a description belongs to. Two western states have more than one: California has three meridians and Nevada two. A mining claim or lease described as "T. 10 N., R. 20 E." without its meridian cannot be located with certainty. In mining claim research, the meridian, township, range, and section are the index for MLRS records, master title plats, and county filings.
Related Terms
PLSS
The Public Land Survey System, the rectangular survey system that divides the public lands into townships, ranges, and sections and serves as the basis for describing them.
Principal Meridian
The north-south survey line through an initial point, run on the true meridian, from which ranges in the Public Land Survey System are numbered east and west.
Base Line
The east-west survey line through an initial point, run on a true parallel of latitude, from which townships in the Public Land Survey System are numbered north and south.
Section Corner
A surveyed corner at the end of a section boundary in the Public Land Survey System, monumented on the ground and controlling the boundaries of the sections it marks.
Cadastral Survey
An official survey that creates, marks, defines, retraces, or reestablishes the boundaries and subdivisions of the public lands, made under the direction of the Bureau of Land Management.