Andrew Ellicott was a skilled mathematician, inventor, and engineer who achieved his greatest fame as a surveyor. Born on 27 January 1754 in Pennsylvania to a Quaker family, Ellicott grew up studying science and its practical uses. He eventually brought his skills to the Deep South and helped the Natchez area become a part of the United States.
Ellicott spent most of his forty-plus years of service to the country determining important boundaries. He finished Charles Mason and Jeremiah Dixon’s work of defining the boundary between Virginia and Pennsylvania—the famous Mason-Dixon Line. He also established the line between New York and Pennsylvania and helped settle a border dispute between Georgia and North Carolina. His exact measurements and attention to detail were all the more remarkable considering that most of his instruments were handmade. Ellicott was the first to record the height of Niagara Falls, superintended the construction of Pennsylvania’s Fort Erie, and helped establish the town there. Perhaps most important, he surveyed Washington, D.C., and helped plan for the nation’s new capital. In 1792 he was appointed surveyor general of the United States.
Diplomatic events brought Ellicott to the Mississippi Valley. On 27 October 1795 the United States and Spain signed the Treaty of San Lorenzo, also known as Pinckney’s Treaty, which granted the United States the free usage of the Mississippi River and set the thirty-first parallel as the northern boundary of Spanish Florida, transferring the Natchez District to the young nation. Soon thereafter, Pres. George Washington appointed Ellicott as commissioner to meet with a Spanish counterpart to set the boundary.
Ellicott arrived in Natchez in February 1797. A strong proponent of American expansion, he immediately pressed Spanish governor Manuel Gayoso de Lemos on when operations would begin. Ellicott further heightened tensions when he defiantly raised an American flag at his encampment.
For more than a year, the Spanish delayed their evacuation from the territory, hoping the treaty would become invalid. Ellicott was caught in a delicate situation, wanting to press the Spanish to follow through on the terms of the treaty yet not wanting to ally himself with the region’s residents who wanted to physically oust the Spanish. After much distress, intrigue, and near revolt, the Spanish finally evacuated the area in March 1798, allowing Ellicott to proceed with the boundary survey.
Ellicott remained in public service as secretary of the land office for Pennsylvania before becoming chair of mathematics at the US Military Academy at West Point. He left briefly to serve his country again when he was called to make astronomical observations associated with the Treaty of Ghent, which ended the War of 1812, but otherwise remained at West Point until his death in 1820.
- Samuel Flagg Bemis, Pinckney’s Treaty: A Study of America’s Advantage from Europe’s Distress, 1783–1800 (1926)
- Jack D. L. Holmes, Gayoso: The Life of a Spanish Governor in the Mississippi Valley, 1789–1799 (1965)
- Catherine VanCortlandt Mathews, Andrew Ellicott, His Life and Letters (1908)
- Clayton Rand, Men of Spine in Mississippi (1940)
- John C. Van Horne, Journal of Mississippi History (August 1983)