Andrew Ellicott (1754–1820) was the foremost surveyor of the early United States. He completed the Mason–Dixon Line, ran the boundaries of nearly a dozen current and future states, surveyed the ground chosen for the new federal capital and carried Pierre L’Enfant’s plan for Washington forward, measured the height of Niagara Falls, and ran the southern boundary of the United States with Spanish Florida. This biography by Lorna Hainesworth follows his life and major surveys from the 1780s through his last boundary work and his years teaching mathematics at West Point, where students nicknamed him “Old Infinite Series.”
The expedition connection is direct. In April 1803, Meriwether Lewis traveled to Ellicott’s home in Lancaster, Pennsylvania, to learn celestial navigation and the practical field surveying he would need in the West, staying about three weeks. Ellicott — himself once a student of Robert Patterson, another of Lewis’s tutors — taught him to fix latitude and longitude with sextant and chronometer. Ellicott’s earlier mapping of the Ohio–Mississippi confluence also informed Nicholas King’s compiled map carried by the Corps of Discovery.
This summary is provided for reference on the Lewis and Clark Research archive; the full article by Lorna Hainesworth is available at the source link.
