One of the most stunning features seen on a cross country flight across the US is the grid structure that has been drawn on the land. Ms Boe, my 11th grade American History teacher, made a point that accurate surveying was the fundamental tool that allowed the expansion of the US along with building a middle class along the way. An accurate and traceable survey finally allowed the defense of property rights for people of limited means.
Many years ago I was driving through the Midwest on country roads. The roads were remarkably straight, but a few times an hour there would be a dead end with right angle turns. Assuming the roads were somehow tied to the surveys, how did this happen? Before giving the answer, it is useful to consider the strange units of measure used by the survey and a bit of history.
The Northwest Ordinance of 1785 was passed to help the US government pay off the enormous debt load it acquired fighting the Revolutionary War. One of the few assets of the new country was unsettled land (never mind that native Americans might be present, but that is another issue), and a mechanism was put in place to sell it.
The bright stroke of the Ordinance came from Jefferson who insisted that a robust survey of the land be made. The survey was to be sufficiently robust that the government, rather than landowners, would be the arbitrator of accuracy.
The units were strange, but their adoption makes an important point. Jefferson (with the support of Hamilton, Madison and Washington), flush with the success of creating a decimal dollar, wanted to decimalize all units and measures. The proposed unit of length was the decimal mile (somewhat longer than the currently used mile), but the adoption of old Anglo-Saxon units insured that the decimal mile would be forever obscure.
The fundamental measurement of length is the rod (sixteen and a half feet). A chain was four rods and a surveyor's chain had that length (a bit of trivia .. a surveyor's "foreman" would stretch the chain until it was straight and a sighting would be taken by the surveyor through a transit to make sure the direction was correct. When it was the surveyor would yell "tally" and a tally pin would be driven into the ground by the foreman.)
In any event one unit of area in Anglo-Saxon England was defined as four rods by four rods and was considered to be the amount of land a strong man could tend to in one day. Forty days worth of work (how biblical) made an acre and 640 acres made a square mile.
A basic unit of the American survey was the township - thirty six square miles. These townships were divided into square mile sections which were sold at auction by the government. The sections were further broken into half sections, quarter sections ... down to quarter-quarter sections (forty acres).
The smallest parcel was very easy to lay out - twenty chains by twenty chains. Railroads were granted huge sections of land to cross the country and sold small parcels in 40 acre lots to settlers. After the Civil War newly freed slaves were considered self sufficient with "40 acres and a mule."
But enough of this and back to the dead ends in the Midwest.
The survey was unified by running a North-South lines known as principal meridians and East-West lines called principal baselines. These linked the work of the many survey teams. Unfortunately the Earth is a sphere and the North end of a township is narrower than the South end. As one moves North this error accumulates and is handled by a remeasure every four townships to force a six mile measurement (the correction line). In the Midwest roads tend to follow survey lines. As you travel along a North-South line the dead end is where the correction was applied.
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