Map Interpretation,
The US Public Land Survey (PLS)
The majority of the land in the US is described under the US Public Land Survey (PLS) System. After independence, the US wanted to dispose quickly of lands in the West (at that time, land between the 13 Colonies and the Mississippi River). Some form of logical, orderly system was inevitable, but the exact form took time to shape. Thomas Jefferson and others eventually worked out a rational, rectangular (squarish) survey, called the Public Land Survey (PLS) system, which was enacted under the Northwest Land Ordinance of 1785 (with later revisions).
The PLS starts out by establishing an x,y coordinate system for
a given area. The north-south line is called a principal meridian,
and the east-west line a baseline. Each baseline is given a unique
name, so that each land parcel can be identified by that name. The
area described based on a principal meridian/baseline pair varies
from a small part of a state (e.g., eastern Ohio, northwestern
California), to several states (e.g., the Fifth Principal Meridian
covers most of Arkansas, Missouri, Iowa, Minnesota, and most of
the Dakotas).
California has three principal meridian/baseline pairs: the San Bernardino Meridian (southern California), Mt. Diablo Meridian (most of northern California), and the Humboldt Meridian (northwestern corner of the state).
The initial point is the intersection of the principal meridian and baseline. From this point, townships are marked off east/west and north/south. Each township is 6 miles on a side, or 36 square miles. Townships are designated on the east-west direction as being a certain number of Ranges east or west of the principal meridian. The township is also a certain number of Townships north or south of the baseline (note the dual use of the term township, as an area and as a coordinate). For example, the township that is just on the northeast corner of the initial point is Township 1 North, Range 1 East, usually abbreviated T. 1 N, R. 1 E. Or T. 3 S, R. 2 W would be the third township south of the baseline and two townships to the west.
Each township had to be divided, since few people could afford 36 mi2. The division was into 36 sections, one square mile each. Rather than using an x,y system here, the sections were simply numbered consecutively from 1 to 36, starting in the northeast corner and snaking around the rows, with 36 at the southeast corner.
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Most land purchases were for less than one section; the Homestead Act of 1863 allowed people to receive one-quarter section if lived on by the claimant. Sections can be broken down into halves or quarters, each part designated by a compass direction. If divided in half, we have either east/west halves, or north/south halves. If divided into quarters, we have the NE, NW, SW, and SE quarters. Quarters can be broken down further if necessary, for example we might have the NE quarter of the SE quarter.
A square mile contains 640 acres, so a quarter section has 160 acres, a quarter-quarter 40 acres, and so on. The typical Midwestern farm used to be a quarter section, or 160 acres. Farms have been consolidated over the past several decades, so the typical farm occupies closer to a square mile, especially in California.
A complete property description must include all of these breakdowns into township, section, and fraction of section (if less than an entire section). A typical property description in a PLS area might read:
USGS topographic maps indicate PLS townships and ranges along the margins. Section and township lines are shown on the map itself with red lines, and sections are numbered in red. You will no doubt notice on some topos that the PLS townships and sections end abruptly in some part of the map. This is common around Santa Rosa. This is because these non-PLS lands were in Land Grants before 1846, when California became part of the US. Remember, once surveyed, never again.
The PLS has had a dramatic impact on the American landscape. Since all land is divided into squares, the landscape itself looks very square. You'll notice this when flying over the middle part of the US, where topography does not interfere with its effects as much. It also contributed to the isolation of farm families in the 19th Century, who lived on their own square farms far from neighbors. Contrast this to French surveyed-lands, where people live much closer together. Our survey system no doubt contributed to the ideal of American individualism.
A final note about the PLS--it's far from a perfect system. There are many irregularities, which are especially noticeable in certain regions. Section and township lines are not always exactly north/south and east/west, and sections are sometimes less than a full square mile (they're then called government lots, or fractional lots). The irregularities derive from several sources:
- Meridians converge to the north, so as surveyors moved north, townships didn't match up with those further south. Often east-west correction lines were set up, along which townships were re-aligned. You'll notice this effect when driving north or south along a country road and you have to take a sudden turn right or left, then turn north/south again after a short distance.
- Surveying in wet or mountainous terrain is difficult, and lines often went astray. Once set up, however, the errors were kept, and lines remained askew.
- Surveyors were paid by the number of sections surveyed, so hurried surveyors weren't always careful surveyors.
- Some surveyors simply weren't careful, or were even staggering-drunk on the job.