Preemption Line

The Preemption Line (also spelled Pre-Emption) divides the Indian lands of western New York State awarded to New York from those awarded to Commonwealth of Massachusetts by the Treaty of Hartford of 1786. It was defined as the meridian (north–south) line from the eighty-second milestone of the Pennsylvania–New York survey line at 76° 57' 58" W northward to Lake Ontario.

By coincidence, the Preemption Line is near the meridian of the Capitol at Washington (77° 00' 33" W of Greenwich), but the popular assumption that the Preemption Line was intended to be on that meridian seems to be a myth, since the District of Columbia had not been surveyed at the time of the 1786 treaty; in fact Benjamin Ellicott helped map and survey the District of Columbia in 1791–1792 and then re-surveyed the Preemption line in 1792 (see below).

The word "preemption" refers to the pre-emptive right that Massachusetts received to negotiate with the Indians—pre-empting New York State, and also to the pre-emptive rights of the two state governments with respect to individuals, who were forbidden to negotiate directly with the Indians without first securing a patent from the respective legislature.

It is bounded on the east (New York portion) by:

It is bounded on the west (Massachusetts portion) by the Phelps and Gorham Purchase.

Time line for the history of the preemption line.

An interesting point is that there are two pre-emption lines: the Old and New (to the east of the Old); the area between is called the Gore (referring to a dressmaker's term for a wedge-shaped piece). This is because very soon after the original survey of 1788 it was suspected that this survey was in error, so a resurvey was commissioned in 1792. It showed that the first surveyors had used defective methods (or, as some allege but not proved fraudulent methods) so that the line, although beginning at the correct Pennsylvania boundary stone, was deflected about 2° west of north, hence the wedge shape (increasing in width to the north). It is not a simple error, however; once the survey was about two miles west of the correct line it then ran closer to true north. The original error was in favor of New York, which issued titles in the Gore; most notably, the current city of Geneva was incorrectly assigned. The new survey was accepted, as it was performed with a high-precision German transit by Benjamin Ellicott, who had just assisted in the initial survey of the District of Columbia (see Boundary Markers of the Original District of Columbia).

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