Andrew Ellicott (1754–1820), surveyor, mathematician, and astronomer, was a native of Bucks County, Pennsylvania, who studied mathematics under Robert Patterson. He moved in 1775 to what became Ellicott City, Maryland, to work in his family’s clockmaking and milling enterprises. Ellicott rose to the rank of major in the Maryland militia during the Revolutionary War. He made mathematical instruments and taught briefly, but soon embarked on a surveying career spanning thirty-five years. Ellicott typically devoted himself to scholarly and domestic pursuits in the winter and to surveying in the warmer months. His most important assignments included work establishing or seeking to set the boundaries between parts of what is now West Virginia and Pennsylvania, Pennsylvania and New York, the United States and Spanish Florida, Georgia and North Carolina, and the United States and Canada. He laid out the town of Erie, Pennsylvania, and roads to it from Reading in the same state. In 1791 Ellicott surveyed the ten-square-mile tract for the nation’s new capital, an endeavor that TJ closely monitored in his capacity as secretary of state. A decade later Ellicott turned down TJ’s offer to appoint him United States surveyor general. Ellicott was the secretary of the Pennsylvania Land Office in Lancaster, 1801–09, and professor of mathematics at the United States Military Academy at West Point from 1813 until his death. He published almanacs, scientific observations, and descriptions of his surveying work, some of which TJ owned. Elected a member of the American Philosophical Society in 1785, Ellicott served as a vice president in 1801 and a counsellor for eighteen years. In 1808 he was elected to the Institut de France (ANB description begins John A. Garraty and Mark C. Carnes, eds., American National Biography, 1999, 24 vols. description ends ; DAB description begins Allen Johnson and Dumas Malone, eds., Dictionary of American Biography, 1928–36, 20 vols. description ends ; Catharine VanCortlandt Mathews, Andrew Ellicott: His Life and Letters [1908; repr. 1997]; Silvio A. Bedini, “Andrew Ellicott, Surveyor of the Wilderness,” Surveying and Mapping 36 [1976]: 113–35; APS description begins American Philosophical Society description ends , Minutes, 22 Jan. 1785, 3 Jan. 1800, 2 Jan. 1801, 6 Jan. 1815 [MS in PPAmP]; PTJ description begins Julian P. Boyd, Charles T. Cullen, John Catanzariti, Barbara B. Oberg, and others, eds., The Papers of Thomas Jefferson, 1950– , 34 vols. description ends , esp. 19:68–71, 24:664, 25:54–5, 449; Sowerby, description begins E. Millicent Sowerby, comp., Catalogue of the Library of Thomas Jefferson, 1952–59, 5 vols. description ends nos. 657, 3779, 4086; JEP description begins Journal of the Executive Proceedings of the Senate of the United States description ends , 1:210, 211, 2:477, 509 [21, 24 May 1796, 17 Feb., 11 Mar. 1814]; Heitman, U.S. Army description begins Francis B. Heitman, comp., Historical Register and Dictionary of the United States Army, 1903, 2 vols. description ends , 2:401; New-York Evening Post, 29 Aug. 1820).

Ellicott had been engaged by Georgia to run its boundary with North Carolina. Unhappy with his discovery that the strip of country ceded from South Carolina to Georgia by way of the United States never had any existence, the governor of Georgia allowed him much less than the sum originally stipulated (Mathews, Andrew Ellicott, 176).