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The Public Land Survey System (PLSS) is the surveying method used historically over the largest fraction of the United States to survey and spatially identify land parcels before designation of eventual ownership, particularly for rural, wild or undeveloped land. It is sometimes referred to as the rectangular survey system (although non rectangular methods such as meandering can also be used). The survey was "the first mathematically designed system and nationally conducted cadastral survey in any modern country" and has been cited as "an object of study by public officials of foreign countries as a basis for land reform." Much of the actual surveying was done in the nineteenth century under a contract system managed by the General Land Office (GLO) resulting in the eventual creation of the State Plane Coordinate System. Required and suggested survey methods have changed over time, as described in a series of Instructions and Manuals issued by the GLO beginning in 1851, although the basic framework has remained substantially unchanged since several experimental methods were first used in Ohio, the first state surveyed under the system (and site of the Beginning Point of the U.S. Public Land Survey). The latest edition of the guidelines is the "Manual of Surveying Instructions (2009)" available from the U.S. Government Printing Office.
Originally proposed by Thomas Jefferson to create a nation of "yeoman farmers", the PLSS began shortly after the American Revolutionary War, when the federal government became responsible for large areas of land west of the original thirteen states. The government wished both to distribute land to Revolutionary War soldiers in reward for their services, as well as to sell land as a way of raising money for the nation. Before this could happen, the land needed to be surveyed.
The Land Ordinance of 1785 was the beginning of the Public Land Survey System. The Continental Congress was deeply in debt following the Declaration of Independence. With little power to tax, the federal government decided to use the sale of the Western Territories to pay off American Revolutionary War debt. It has been expanded and slightly modified by Letters of Instruction and Manuals of Instruction, issued by the General Land Office and the Bureau of Land Management and continues in use in most of the states west of Pennsylvania, south to Florida, Alabama, and Mississippi, west to the Pacific Ocean, and north into the Arctic in Alaska.
The original colonies (including their derivatives Maine, Vermont, Tennessee, Kentucky and West Virginia) continued the British system of metes and bounds. This system describes property lines based on local markers and bounds drawn by humans, often based on topography. A typical, yet simple, description under this system might read "From the point on the north bank of Muddy Creek one mile above the junction of Muddy and Indian Creeks, north for 400 yards, then northwest to the large standing rock, west to the large oak tree, south to Muddy Creek, then down the center of the creek to the starting point."
Particularly in New England, this system was supplemented by drawing town plats. The metes-and-bounds system was used to describe a town of a generally rectangular shape, 4 to 6 miles (~6 to 10 km) on a side. Within this boundary, a map or plat was maintained that showed all the individual lots or properties.
There are some difficulties with this system:
In addition this system didn't work until there were already people on the ground to maintain records. In the 1783 Treaty of Paris recognizing the United States, Britain also recognized American rights to the land south of the Great Lakes and west to the Mississippi River.
The Continental Congress passed the Land Ordinance of 1785 and then the Northwest Ordinance in 1787 to control the survey, sale, and settling of the new lands. The original 13 colonies donated their western lands to the new Union, for the purpose of giving land for new states. These include the lands that formed the Northwest Territory, Kentucky, Tennessee, Alabama, and Mississippi. The state that gave up the most was Virginia, whose original claim included most of the Northwest Territory and Kentucky, too. Some of the western land was claimed by more than one state, especially in the Northwest, where parts were claimed by Virginia, Pennsylvania, and Connecticut, all three of which had claimed lands all the way to the Pacific Ocean.
The Beginning Point of the U.S. Public Land Survey is located at a point on the Ohio-Pennsylvania border between East Liverpool, Ohio and the Pittsburgh metropolitan area, on private property. A National Historic Landmark marker commemorating the site lies on the side of a state highway, exactly 1,112 feet (339 m) to the north of the point.
Ohio was surveyed in several major subdivisions, collectively described as the Ohio Lands, each with its own meridian and baseline. The early surveying, particularly in Ohio, was performed with more speed than care, with the result that many of the oldest townships and sections vary considerably from their prescribed shape and area. Proceeding westward, accuracy became more of a consideration than rapid sale, and the system was simplified by establishing one major north-south line (principal meridian) and one east-west (base) line that control descriptions for an entire state or more. For example, a single Willamette Meridian serves both Oregon and Washington. County lines frequently follow the survey, so there are many rectangular counties in the Midwest and the West.
The system is in use in some capacity in most of the country, but large portions use other systems.
The territory under the jurisdiction of the Thirteen Colonies at the time of independence did not adopt the PLSS, with the exception of the area that became the Northwest Territory and some of the Southern states. This territory is now Georgia, Connecticut, Delaware, Kentucky, Maine, Maryland, Massachusetts, New Hampshire, New Jersey, New York, North Carolina, Pennsylvania, Rhode Island, South Carolina, Tennessee, Vermont, Virginia, and West Virginia.
Maine uses a variant of the system in unsettled parts of the state.
Other major exceptions to PLSS are
The surveying of any regional area, such as a state or two, is a multi-step process. First, two controlling survey lines are established: a baseline, which runs east-west and a principal meridian, which runs north-south (Fig. 1). The locations of the two are determined by a previously chosen initial point, where they originate and thus intersect. Next, at a defined distance interval, commonly 24 or 30 miles (48 km) depending on the year and location, standard parallels of latitude are established parallel to the baseline. The meridian, baseline and standard parallels thus established form a lattice upon which all further surveying is then based. Subsequent work divides the land into survey townships of roughly 36 square miles (~93 km2) or 6 miles (~9.7 km) on each side. This is done by the establishment of township and range lines. Township lines run parallel to the baseline (east-west), while range lines are true meridians and thus run north-south; each are established at six mile (10 km) intervals. Lastly, townships are subdivided into 36 sections of approximately one square mile (640 acres, ~2.6 km2) and sections into four quarter-sections of 0.25 square mile (160 acres, ~0.65 km2) each. (See descriptions and figures illustrating the system). The intersection of a township line (or baseline) with a range line (or principal meridian) constitutes a township corner, of a section line with any other type of line a section corner, and a point halfway between any two section corners a quarter corner. The federal government typically surveyed only to this quarter-section level, the subdivision of smaller parcels being carried out subsequently by private surveyors after original sale.
Because the survey design is two-dimensional (rectangular), while the actual earth is three-dimensional (~ spherical), adjustments to land areas must be made periodically to prevent error propagation; not all sections can be one square mile nor can all townships be exactly 36 square miles. More specifically, all north-south running lines (all range lines and half of all section lines), as with the prime meridian, are always established with reference to true, geodetic north. But it is a physical impossibility to meet this condition and still maintain a rectangular land grid, because such lines converge on the north pole—they are meridians.
These adjustments are done at two different scales. At the small scale (within a township) it is done by starting the sectional surveys (township "subdivisions") in the southeast corner and moving progressively toward the northwest corner. The algorithm used is to move northward to establish the six eastern-most sections (and quarter-sections), then move west at one mile intervals, repeating this process, until the western side of the township is reached. The result of this is that the northernmost and westernmost tiers of sections—-11 in all—-are thus allowed to deviate from one square mile, but the other (southeasterly-most) 25 sections are not. This method accommodates the curvature problem within a township, and it also allows for any errors made during the surveying itself—-which were nearly unavoidable due to the physical difficulty of the work and the crude equipment used—-without overly compromising the basic rectangular nature of the system as a whole. At the larger multiple township scale, the standard parallels mentioned above allow a longitudinal re-setting of township corner locations, so that townships widths do not continually decrease as one proceeds north (and is in fact the primary reason for their establishment). Thus, corrections for curvature of the earth exist at two separate spatial scales—a smaller scale within townships, and a larger scale between multiple townships and within standard parallels.
A specific and terse location descriptor is always used, in which the townships and sections are indexed based on (1) the township's position relative to the initial point, (2) the section's location within the designated township, and (3) the principal meridian reference. Township, range, and section are abbreviated as T, R, and S, respectively, and cardinal bearings from the initial point by N, S, E, and W; each principal meridian also has its established abbreviation. Thus, for example, the description "T1SR20E S13 MDM" reads as follows: Township 1 South, Range 20 East, Section 13, Mount Diablo Meridian. That is, the 13th section in the first township south of the baseline (in this case, the Mount Diablo Baseline) and the 20th township east of the principal meridian (the Mount Diablo Meridian). Since township and range lines are six miles apart, the "T1SR20E" part of the designation instantly places the location somewhere between zero and six miles south of the baseline, and 114 and 120 miles east of the principal meridian. Knowing how sections are numbered within townships, we identify section 13 as therefore occupying the one square mile located 2 to 3 miles south, and 119 to 120 miles east, of the Mount Diablo initial point (in central California). Note that the sections within a township are numbered in an unconventional, Boustrophedon pattern (Fig. 2), in which alternating rows are numbered in opposite directions, starting from section 1 in the northeast corner and ending with section 36 in the southeast corner, as per Figure 2. Therefore, section 13 is adjacent to the eastern range line of the designated township. Numbering in this pattern ensures that numerically sequential sections within the same township are physically adjacent, and share colinear boundaries.
Distances were always measured in chains and links, based on Edmund Gunter’s 66 foot measuring chain. The chain--an actual metal chain--was made up of 100 links, each being 7.92 inches (201 mm) long. Eighty chains constitute one U.S. Survey Mile (which differs from the International Mile by a few millimeters). There were two chainmen, one at each end, who physically made the measurements, one of them typically also acting as "compassman" to establish the correct bearing at each chain placement. In forested areas, it was essential for rapid progress and accuracy that the lead chainman follow the correct bearing at all times, since no straightening of the chain was possible without backtracking around trees and re-measuring. It was also necessary to keep the chain level, since all surveying distances are based on the horizontal, not slope, distance. In steep terrain, this meant either shortening the chain, or raising one end of the chain relative to the other, or both. In areas where measuring by chain was not possible, such as extremely steep terrain or that with water obstructions, distances were calculated by triangulation.
Monumentation is the establishment of permanent on-the-ground objects that mark exact locations of surveyed points and lines. They are the legally binding markers used for setting property lines and as such are the culminating work of any survey. They consist of both corner monuments as well as nearby accessory objects that "witness" to them. Witness objects allow subsequent surveyors and landowners to find the original corner monument location should the actual monument itself be destroyed. It was not uncommon for squatters or homesteaders to destroy corner monuments if they felt the patenting of the land would threaten their residence on it. For this reason, destruction of corner monuments, or their accompanying witness objects was, and still is, a federal offense.
At corners, corner monuments are established to mark their exact location on the ground. As with most PLSS specifications, those for corner monumentation also changed over time. In the 19th century, monuments were commonly a rock pile, a wooden post, or a combination of the two. Trees could be used if the corner happened to fall at the exact spot where one grew. In the 20th century, steel pipes with caps, supported by mounds of rock, became required (e.g. Fig. 4). Witnesses can be trees, rocks, or trenches dug in the ground; their exact locations relative to the corner, and the markings made on them, are also recorded in the surveyor's official field notes. Witness trees at corners are more commonly referred to as bearing trees because the exact distance and bearing from the corner, to them, was required to be recorded (as well as the taxon and diameter).
On each bearing tree, two blazes were typically required, one about chest height and easily visible, and one at ground level (in case the tree were illegally cut, the stump remaining). On the exposed wood of the blaze, surveyors were required to inscribe, with wood chisels, township, range and section information, on typically either two or four bearing trees, if they were within some reasonable distance of the corner (unspecified early on but later set at a maximum of 3 chains (178 feet, 60 meters) away). Bearing trees are of vital importance not just for these land boundary purposes, but also for their use by ecologists in the estimation of historic forest vegetation conditions before settlement, and large scale human disturbance, of the land. No other data set comes close to providing this estimate of original forest composition and structure, and the data have accordingly been used very heavily.
Along survey lines, monumentation was much less elaborate, consisting primarily of only the blazing and some very simple scribing of trees directly on, or very close to, the survey line. The purpose was simply to help retrace a surveyed line should that become necessary. It was also additional proof that the line had in fact been run correctly, especially in those cases where the blazed "line tree"'s pertinent information (species, diameter and distance from previous corner) was recorded in the field notes, as they often were required to be.
What was to be observed and recorded by the surveyors during the execution of the work varied over time. Furthermore, how well individual surveying parties actually met the requirements or recommendations at the time, also varied. The following is a list of the more commonly required landscape and surveying items that were either required or requested be noted, over much of the nineteenth century.
The following table indicates some distance and area conversions in the PLSS:
|Quadrangle||24 by 24||576||368,640||1,492||Usually 16 townships|
|Township||6 by 6||36||23,040||93||Usually 36 sections|
|Section||1 by 1||1||640||2.6|
|Half-section||1 by 1⁄2||1⁄2||320||1,294,994||1.3|
|Quarter-section||1⁄2 by 1⁄2||1⁄4||160||647,497|
|Half of quarter-section||1⁄2 by 1⁄4||1⁄8||80||323,749|
|Quarter of quarter-section||1⁄4 by 1⁄4||1⁄16||40||161,874|
|Black Hills Meridian||1878||South Dakota|
|Copper River Meridian||1905||Alaska|
|Fifth Principal Meridian||1815||Arkansas, Iowa, Minnesota, Missouri, North Dakota & South Dakota|
|First Principal Meridian||1819||Ohio & Indiana|
|Fourth Principal Meridian||1815||Illinois|
|Fourth Principal Extended Meridian||1831||Minnesota & Wisconsin|
|Gila and Salt River Meridian||1865||Arizona|
|Huntsville Meridian||1807||Alabama & Mississippi|
|Kateel River Meridian||1956||Alaska|
|Michigan Meridian||1815||Michigan & Ohio|
|Mount Diablo Meridian||1851||California & Nevada|
|New Mexico Principal Meridian||1855||Colorado & New Mexico|
|Montana Principal Meridian||1867||Montana|
|Salt Lake Meridian||1855||Utah|
|San Bernardino Meridian||1852||California|
|Second Principal Meridian||1805||Illinois & Indiana|
|Sixth Principal Meridian||1855||Colorado, Kansas, Nebraska, South Dakota & Wyoming|
|Saint Helena Meridian||1819||Louisiana|
|Saint Stephens Meridian||1805||Alabama & Mississippi|
|Tallahassee Meridian||1824||Florida & Alabama|
|Third Principal Meridian||1805||Illinois|
|Willamette Meridian||1851||Oregon & Washington|
|Wind River Meridian||1875||Wyoming|
Based on the BLM manual's 1973 publication date, and the reference to Clarke's Spheroid of 1866 in section 2-82, the coordinates listed are believed to be in the NAD27 datum.
The Pacific Railroad Act of 1862 (signed by President Abraham Lincoln) was the first major land grant specifically for the transcontinental railroad. This act provided surveyed, public lands for a railroad right-of-way to build rail systems, and millions of acres to raise the capital needed to build and maintain the future railways. Ten square miles of land on each side of the proposed rail track were granted for every one mile of completed railway. The U.S. Public Land Survey System was utilized for measurement. Every one-mile railway completed was akin to a section. If the railway ran predominantly east and west, a 10-mile (16 km) range of one square mile sections were allotted on each side of the 400-foot (120 m) right-of-way. If the railway ran predominantly north and south, a 10-mile (16 km) township of one square mile sections were allotted on each side of the 400-foot (120 m) right-of-way. The land was granted in alternating sections (one square mile). Each odd numbered section going to the railroad company. Each even numbered section kept by the government. This created a checkerboard pattern along proposed rail way. This was supposed to guarantee that railroad access would increase the value of not only the railroad granted sections, but also the government owned sections in the checkerboard. The system was devised by Senator Stephen A. Douglas, with political support from Senator Jefferson Davis.
Under the 1785 act, section 16 of each township was set aside for school purposes, and as such was often called the school section. Section 36 was also subsequently added as a school section in western states. The various states and counties ignored, altered or amended this provision in their own ways, but the general (intended) effect was a guarantee that local schools would have an income and that the community schoolhouses would be centrally located for all children. An example of land allotments made specifically for higher education is Ohio's College Township.
There were numerous incidents of fraudulent or bad surveying reported, arguably in nearly every state. The remote nature of the land being surveyed certainly enabled the opportunity for fraud to occur. The most notorious, large scale, and costly fraud was perpetrated by the Benson Syndicate, operating primarily in California in the 1880s.
The U.S. Public Land Survey System is considered one of the major points of contention in the adoption of the metric system in the United States. The U.S. Public Land Survey System has used the Gunter's chain as a basic measurement.
"...the measurements of every plot of ground in the United States have been made in acres, feet, and inches, and are publicly recorded with the titles to the land according to the record system peculiar to this country." —Franklin Institute of Philadelphia (1876). Because of this, redefining property boundaries could create a large amount of legal issues and property owner confusion. Many local zoning laws are defined in feet/square feet. Conversion of units for surveyors are not always simple and complex decisions are frequently required (non-universal conversion factors, soft/hard conversions, number rounding).
As roads have typically been laid out along section boundaries spaced one mile (1.6 km) apart, growing urban areas have adopted road grids with mile-long "blocks" as their primary street network. Such roads in urban areas are known as section line roads, usually designed primarily for automobile travel and limited in their use for non-motorized travel. In post-World War II suburbs, commercial development has largely occurred along and at intersections of arterials, while the rest of the former square-mile sections have generally filled with residential development, as well as schools, religious facilities, and parks. One example of this is famous Mile Road System of Detroit, Michigan.
Occasionally, and more frequently in a metropolitan region's inner postwar suburbs than in outer areas, arterials are located at approximately half-mile intervals. This strictly regimented urban (or suburban) structure has coincided with the similarly strict practice of Euclidean zoning (named after the town of Euclid, Ohio, which won a 1926 Supreme Court case Village of Euclid, Ohio v. Ambler Realty Co., which established the constitutionality of zoning). In Euclidean zoning, use of a property is dictated and regulated by zoning district, the boundaries of which are often based on locations of arterials.
West of the Appalachians, road systems frequently follow the PLSS grid structure (see illustrations of Nebraska vs North Carolina on left). The results can be 90-degree intersections and very long stretches of straight roads.
The land system is an important part of American history and culture. Among other things, the stock phrases "lower 40", "front 40", "back 40", and "40 acres and a mule", which are sometimes heard in American movies, reference the quarter-quarter section.
Act of Congress, February 24, 1863, granted sections 16 and 36 of each township for the benefit of the common schools