The Public Land Survey System
PLSS Townships
PLSS Townships are the primary unit of survey for the PLSS, nominally six miles on a side, usually containing 36 sections. PLSS Townships are numbered from base lines and principal meridians. This feature class provides the polygons for the PLSS Townships. The diagram below illustrates the basic PLSS Township referencing and numbering.
A fairly typical set of Townships with their sections is shown below. The Townships are designated with the Township (Tier) number and direction and the range number and direction. For example the Township in the middle is Township 30 North Range 31 East.
But to be complete the Townships also need a principal meridian reference. The list of Principal Meridians (PM) and their national two digit codes are listed at the end of this article. A map illustrating the principal meridians can be found at this link
https://www.blm.gov/sites/blm.gov/files/meridianmap09_1.jpg (accessed July 2020)
A detailed text describing the history and development of each principal meridian and baseline (Initial Points) can be found at this page (Click on Al White for a link to the book).
http://www.pmproject.org/index.htm (accessed July 2020)
The attributes for a PLSS Township more fully described in the nationalcad.org web page and are listed below. The field lengths for the attributes may be adjusted and the field names and intended content are the focus of the implementation standard. This is a list of all identified possible attributes recognizing there is duplication in the content. A state or county may want to modify these attributes to reduce the data entry and duplication.
State Abbreviation. State abbreviation code two letter postal code
Principal Meridian Code. Principal meridian code from the BLM PM Code list
Principal Meridian Text. Principal meridian name as a text
Township number. The Township Number indicates the number of rows of townships, north or south from a Public Land Survey System Origin.
Township fraction. Township Fractions are created when there are gaps between surveyed Township boundaries or due to excess size in Townships that arose from executing original surveys.
Township direction. The direction of a row of Townships from a Public Land Survey System Origin. These are typically North and South in the West but may be East and West in Ohio
Range number. The Range Number indicates the number of columns of townships, east or west from a Public Land Survey System Origin.
Range fraction. Range Fractions are created when there are gaps between surveyed Township boundaries or due to excess size in Townships that arose from executing original surveys.
Range direction. The direction of a column of townships from a Public Land Survey System Origin. These are typically East or West in the west but may be north or south in Ohio
Township Duplicate. If there are multiple townships in a Public Land Survey System Origin, State and Survey Name, the Township Duplicate Status is used to establish uniqueness. When more than one Public Land Survey System Township has the same Township and Range numbers and directions and fractions, and is in the same State, this attribute is used to distinguish among duplicate values. A is the first duplicate, B the second etc. A 0 in this field indicates no duplicates
Township Identifier. Concatenation of the principal meridian, township, range, and duplication code that form a unique id.
Township Label. Township label that is used for cartographic output or web display
Survey Name for PLSS Areas. A common or otherwise recognized name for a portion of area of a PLSS Survey, for example the refugee lands in Ohio or in cases where a PLSS Township has a recognized name.
Survey Type Code. Code of the type of special survey, typically these are the codes described in the BLM data collection as survey type codes. For PLSS Townships these codes will be U, Unsurveyed Protracted and Z, unsurveyed unprotrated
Survey Type Text. Special survey type text description, for interpreting the codes
Source Date. The date of the source document
Source Reference. The reference to the source document could be a reference to a map or plat or a deed. This could include document type.
Why is the state included in the PLSS Township Table? This is because in some cases, notably along the Colorado-Kansas boundary, the Principal Meridian, numbers and directions for two “columns” of townships are repeated, with the only unique designation being the state. Also many state boundaries in the west are coincident with Township boundaries. Townships that are split by state lines are divided into two polygons for the standardized data.
The survey type is used to identify unsurveyed townships and townships that have been defined on a protraction diagram, which is a plan of survey. If the survey type is blank, the township boundary has been surveyed. The source date and source reference are optional fields that can be used to identify the first date of survey and the source document, typically a General Land Office (GLO) or BLM plat.
The figure below illustrates some fractional or half township and half ranges in Nevada. Fractional parts can be half, quarter, or three quarters. Fractional townships may not be familiar to many of the PLSS data users, but they occur in almost every state.
The other exceptional coding are the duplicate townships. This happens when the Township tier, range, and PM are duplicated within a state.
The image below is from a portion of the Ohio PLSS from the Ohio River Base PM. The Township labels have the duplicate code at the end. The first duplicate has an A indicating that another Township with the same designation exists. The convention is to assign the first duplicate code, A, to the township closest to the baseline or PM.
