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 native sovereign tribes--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 sovereign tribes without first securing a patent