Andrew Ellicott (1754-1820) was born in Pennsylvania and reared in Ellicott Mills, Maryland, which was founded by his father. Ellicott was the foremost surveyor of his day. He conducted numerous surveys to establish state and territorial boundaries, including the boundary between the United States and the Spanish possessions in Florida. He also surveyed the site for the nation’s capital at Washington, D.C. Ellicott elevated American surveying and cartography to a new level of precision and accuracy.
The Journal of Andrew Ellicott (1803) includes a map of the mouth of the Mississippi River, two maps of the Mississippi below the mouth of the Ohio River, and two maps of the Ohio. In addition, Ellicott mapped the upper Mississippi River to the Great Lakes and located the position of the mouth of the Missouri River quite accurately. An appendix to the Journal contains many examples of his measurements, astronomical observations, and detailed calculations from his surveys in Florida and along the Mississippi River.The Journal, which was published at the time of the Louisiana Purchase, is also noteworthy because Ellicott presents an argument for the United States’s acquisition of Louisiana as a way to keep the western states in the Union.
When Albert Gallatin commissioned Nicholas King to produce a new map of North America for the Lewis and Clark Expedition, he instructed the mapmaker to incorporate Ellicott’s work on the Mississippi River. In planning the expedition to the West, Thomas Jefferson turned to Ellicott for advice. Jefferson knew that no other American had more knowledge or experience than Ellicott in making astronomical and field observations under trying conditions. Ellicott supplied Jefferson with a list of the equipment that he thought should be taken on the expedition. He also instructed Meriwether Lewis in the use of the sextant and octant, regulated Lewis’s chronometer, and devised a new type of artificial horizon for making field observations on the expedition.