Progress of the Triangulation Between the Ohio and Mississippi Rivers

Detailed chart showing survey progress along the 39th parallel between the Ohio and Mississippi Rivers.

An excellent map of the Ohio and Mississippi Valley regions showing detailed progress of the land survey between the two mighty rivers along the 39th parallel. Surveyors would use triangulation to measure angles and distances between static points. These points, or stations, are depicted by icons on the map, in addition to the meridians and landmarks used by the surveying team.

Five states and several major cities including Cincinnati, Louisville and St. Louis are covered by the map. Published in the annual report of the United States Coast and Geodetic Survey in 1890.