Background Information about the PLSS from the USGS
Excerpted from
USGS Part 3: Attribute Coding,
Standards for Digital Line Graphs (DLG-3)
Appendix 3.11.A - Background Information on the Public Land Survey System
Introduction
All lands in the public domain are subject to subdivision by a rectangular system
of surveys called the Public Land Survey System (PLSS), established and regulated
by the Bureau of Land Management. The original public domain includes the land ceded
to the Federal Government by the Thirteen Original States, supplemented with acquisitions
from native Indians and foreign powers. It encompasses major portions of the land
area of 30 western States.
Under Congressional mandate, cadastral surveys of public lands were undertaken to
create parcels suitable for disposal by the Government. The PLSS was developed for
this purpose. The PLSS is a rectangular survey system that typically divides the
land into 6-mile square townships, which are further subdivided into 1-mile square
sections. The extension of the rectangular system of surveys over the public domain
has been in progress since 1785. These surveys form the basis of patents issued
when public lands pass out of Federal ownership.
Certain lands were excluded from the public domain and not subject to survey and
disposal. These lands include the beds of navigable bodies of water, national installations
such as military reservations and national parks, and areas such as land grants
that had already passed to private ownership prior to subdivision by the Government.
Data describing the PLSS is required by Federal surface and mineral management agencies,
as well as any organization concerned with land ownership in the 30 western States
that were formed from the public domain. Additionally, many agencies have encoded
natural resource or environmental inventory data based on the PLSS.
The Rectangular System of Surveys
The rectangular system of surveys was devised to subdivide public domain lands.
It divides the land into townships 6-mile square by north and south lines that run
according to the true meridian and by others crossing the north and south lines
at right angles. Townships are, in turn, subdivided into sections of, as nearly
as possible, 640 acres by parallel lines that run east to west and south to north
at 1-mile intervals. Corner monuments are placed along all lines as they are surveyed
at 1/2-mile (quarter-section) intervals. The monumentation is intended to establish
a permanent marking of the lines and to fix the corner positions so that the location
of the surveyed lands can always be definitely known.
With respect to the ideal rectangular plan, a survey of the public lands is accomplished
by establishing, in order, the following:
Independent initial point
This is the point from which the survey of the principal meridian and base line,
controlling the survey of the public lands in a given area, is initiated. There
are 46 separate surveys in the nationwide system. Of these, only eight in Ohio and
Indiana (commenced between 1785 and 1805) have no initial point as defined.
Principal meridian
This is a line extending north and south along the astronomic meridian passing through
the initial point. It serves as the origin for the survey of township boundaries
along the parallels.
Base line
This is a line extending east and west along a true parallel of latitude passing
through the initial point. It serves as the origin for the survey of meridional
township boundaries.
Standard parallels (correction lines)
These are auxiliary governing lines that extend east and west from the Principal
Meridian, generally at intervals of 24 miles (four townships) north and south of
the base line. In many surveys run before 1850, correction lines were run at intervals
of 30, 36, or 60 miles. Standard parallels are used to take up error in the rectangular
plan caused by the convergence of meridians.
Guide meridians
These are auxiliary governing lines that are projected north from points established
on either the base line or standard parallels, generally at intervals of 24 miles
east and west of the principal meridian. Guide meridians terminate at the point
of intersection with another standard parallel.
Township exteriors
These are lines surveyed at 6-mile intervals that conform to meridians and parallels
within established limits. Meridional township boundaries (range lines) are run
from south to north and terminate at the point of intersection with a standard parallel.
Latitudinal township boundaries (township lines) are run from east to west through
corners established on the meridional lines. Townships are numbered to the north
and south commencing with number 1 at the base line, and with range numbers to the
east and west commencing with number 1 at the principal meridian. The township number
is used in conjunction with the range number to indicate the coordinates of a particular
township with respect to the initial point.
Subdivision of townships
The south and east boundaries of a township are normally the governing lines of
subdivisional surveys. Meridional section lines are initiated at the section corners
at the south boundary of the township and are run north parallel to the east boundary.
They are not continued north beyond a section corner until the connecting latitudinal
section lines have been surveyed. Latitudinal section lines are run west to east
parallel to the south boundaries of the respective sections. Any fractional measurement
is placed in the north or west 1/2 mile of the township. A normal township is divided
into 36 sections numbered commencing with number 1 in the northeast section of the
township, proceeding west to section 6, then south to section 7, then east to section
12, and so on, to number 36 in the southeast section.
Half townships may be created in instances where the distance between the regular
position of township boundaries is so great that the application of normal rules
of subdivision would result in sections elongated in excess of 120 chains (7,920
feet). Half ranges may be created in instances where the distance between the regular
position of township boundaries is so great that the application of normal rules
of subdivision would result in sections elongated in excess of 120 chains (7,920
feet).
Subdivision of sections
Subdivision of sections into aliquot parts or irregular lots is controlled by the
previously established section and quarter-section corners. This subdivision may
be accomplished by field methods or protracted on the official plat. Subdivision
lines and corners are shown on quadrangle maps, usually to the section level with
some quarter section corners shown, to the extent that their positions can be determined
from evidence on the ground. During field work, enough corners are located to accurately
position the network of public land lines from official plats. Although the PLSS
is mapped to meet National Map Accuracy Standards, its depiction is not intended
to be official or authoritative; it is presented as useful reference information.
The only legal basis for determining land boundaries remains the original survey.
Survey Corners
Survey corners are points on the surface of the Earth that represent extremities
of a subdivision of the public lands, generally at the intersection of two or more
surveyed lines. The classification of a corner describes the relative corner location,
type of survey, or the controlling aspects of the corner. A survey corner is identified
by unique symbology or labeling on the map only when the monumented point has been
recovered in the field.
The following is a list of the types of survey corners found on USGS quadrangle
maps:
Angle point
This is a point on a survey where the alignment or boundary deflects from a straight
line.
Amended monument
A survey monument whose position no longer marks the true position for the corner,
but which is connected by course and distance to the new corner. There are two primary
applications of amended monuments:
(1) If another survey such as a mineral survey, homestead entry, small holding claim,
or right of way or reservoir survey has been tied to a monument that has been found
to be out of position, the monument is marked "AM" and connected by course and distance
to a new, correctly positioned monument, and (2) If a recovered closing corner is
not at the true point of intersection of the line it is closing to, a new monument
will be placed at the true point of intersection and the old monument will be marked
"AM" and connected by course and distance.
Land grant or other special survey corner
A monumented point on a land grant, tract, donation land claim, U.S. Survey, Homestead
Entry Survey, or Indian Allotment.
Meander corner
The beds of navigable bodies of water are not public domain and are not subject
to survey and disposal by the United States. At every point where a section line
intersects the banks of such a feature, a meander corner is established, and a metes
and bounds traverse, called a meander line, is run to segregate the water area from
the public lands. Meander lines are not mapped.
Quarter-section corner
Quarter-section corners are found at the extremity of a quarter-section boundary,
theoretically located halfway (40 chains)between section corners. Normally, quarter-section
corners are not searched for or plotted unless there is a bend in the line at the
corner or the section corners on either side cannot be recovered.
Section Corner
A section corner is established at the extremity of a PLSS section boundary, where
two or more section lines meet or cross. It is surrounded by one or more distinct
sections.
U.S. Mineral Monument and U.S. Location Monument
This is a monumented reference for one or more mineral surveys or for an isolated
special survey. The monument is established during surveys of the irregular boundaries
of mining claims when no public land corners have been established in the vicinity.
When the public land surveys are subsequently extended to the area, the mineral
monument is tied to a regular section corner. This type of monument may also be
used in any situation where no corner of an existing survey is available to provide
a satisfactory connection for an isolated special survey. In most cases a the monument
does not fall on a public land line.
Witness corner
A witness corner is established if the true corner cannot be marked in the usual
manner because of obstructions or difficult terrain. It is located on the section
line within 10 chains (660 feet) or anywhere within 5 chains (330 feet) of the actual
corner. Normally, only one witness corner is established in each instance. For example,
a witness corner is commonly established on secure ground when the true position
of a meander corner falls at a point where the monument would likely be destroyed
by the effects of tide, waves, or ice.
Witness point
This is a monumented point on a survey line marking an important location remote
from and not related to a regular corner (for example, a road or stream crossing).
Survey Lines
Survey lines in the PLSS category represent the build up of the land net from the
section corners whose monuments have been recovered in the field. The accuracy of
the section lines depends on the relative accuracy and density of the recovered
section corners.
Solid lines connect reliable section corners and represent survey lines plotted
to meet National Map Accuracy Standards (40 feet at the 1:24,000 scale). Dashed
section lines connect questionable section corners and represent survey lines that
do not meet National Map Accuracy Standards, but are plotted within 200 ft at 1:24,000-scale.
The Bureau of Land Management has defined protracted land lines for all areas of
Alaska not yet subdivided by ground surveys and some other areas in the continental
United States. The unsurveyed land lines represent theoretically perfect subdivisions.
Protracted land lines have been shown as solid gray lines on Alaska quadrangle maps.
The current symbol for protracted land lines is a solid red line. The protracted
land lines for all suspended and unsurveyed townships in the conterminous United
States are not shown at the 1:24,000 scale unless they are provided by the Forest
Service for portrayal on quadrangle maps produced through the single edition initiative.
Protracted land lines are shown by dashed red lines on 1:100,000-scale maps. Land
lines may be omitted from maps in public land States when they have not been established
by survey or where there is insufficient field evidence to position the land net
to established standards. A note in the map margin explains the reason for the omission.
Survey Areas
The States within the public domain contain a variety of surveys, such as land grants,
lands subdivided by rectangular surveys, and lands subdivided by special surveys.
Specific types of survey areas within the public domain that are shown on USGS quadrangle
maps are:
PLSS Area
An area of land that was part of the original public domain and which was subject
to subdivision by the Public Land Survey System. The PLSS is a rectangular survey
system that typically divides the land into 6- mile square townships, which are
further subdivided into 1-mile square sections.
Homestead Entry Survey
A Homestead Entry is an entry under the U.S. laws for the purpose of acquiring title
to a portion of the public domain under the Homestead laws. A Homestead Entry is
a metes and bounds survey entered under the Act of June 11, 1906 as amended. Homestead
Entries are not mapped unless they define the limits of the land net.
Donation Land Claim
Tracts of land, 320 or 640 acres in size, were allocated to settlers in the Oregon
Territory (Oregon and Washington) who had resided on and cultivated the land for
4 years under the Donation Act of September 27, 1850; to settlers in Florida under
the Act of August 4, 1842; and to settlers in the New Mexico Territory (New Mexico
and Arizona) under the Act of July 22, 1854. These tracts were part of the original
public domain and were surveyed prior to the rectangular surveys. Donation Land
Claims are not mapped unless they define the limits of the land net.
Land Grant
A land grant is an area of land to which title was conferred by a predecessor government
and confirmed by the U.S Government after the territory in which it is situated
was acquired by the United States. These lands were never part of the original public
domain and were not subject to subdivision by the rectangular surveys.
Private Extension of the Public Land Survey
The term "private" refers to any public land survey not performed by or contracted
by the Bureau of Land Management. They include, for example, Bureau of Indian Affairs
surveys on Indian lands. These areas are also assigned origin of survey, township,
range, and section number parameters as appropriate.
Tract
The term tract is used to mean a parcel of land that lies in more than one section
or cannot be identified in whole as part of a particular section. Tract boundaries
are not mapped unless they define thel limits of the land net.
United States Survey
A metes and bounds survey executed to comply with one of various regulations for
entry of public lands in Alaska. U.S. Surveys are not mapped unless they define
the limits of the land net.
Indian Allotment
An allocation of a parcel of public lands or Indian Reservation lands to a native
American for his or her individual use in the lower 48 States. Indian Allotments
are not mapped unless they define the limits of the land net.
Irregular Rectangular Surveys in Ohio and Indiana
The rectangular system of surveys was in its initial stage of development when the
State of Ohio was surveyed, beginning in 1785. Because the current system of principal
meridians and baselines was not yet established, the Ohio surveys used a number
of different reference meridians and base lines. Eight public land surveys were
conducted having no initial point as an origin for both township and range numbers.
These include seven surveys in Ohio and one in Indiana. They commenced between 1785
and 1805, a period when the laws prescribing the subdivision of the public domain
were in flux. Although rectangular in nature, these surveys do not strictly conform
to the current plan. Within several surveys, townships depend on crooked rivers
for base lines. This causes offsets in the township tiers and irregular sequences
of numbering. In addition, the subdivision of townships is not consistent. The current
system of numbering sections within a township was not adopted until passage of
the Land Act of May 18, 1796. Prior to this time, the original Ordinance of May
24, 1785, applied, in which sections were numbered commencing with number 1 in the
southeast corner of the township, proceeding north to section 6, then continuing
with section number 7 in the southernmost section of the next column to the west,
and proceeding north to section 12, and so on, to number 36 in the northwest section.
