governor Thomas McKean and took a position as Secretary of the Pennsylvania Land Office. The family moved to Lancaster, Pennsylvania, and Ellicott seemed content with a clerk's job that left him enough time for his own scientific and private interests and that provided a steady income for the family. The Andrew Ellicott House, in Lancaster where he resided from 1801 to 1813, was listed on the National Register of Historic Places in 1972, by the National Park Service. Also in 1803, President Jefferson engaged Ellicott as a mentor and teacher for Meriwether Lewis, one of the leaders of the Lewis and Clark Expedition that was to start the following year. From April to May 1803, Lewis stayed at Ellicott's home and studied survey techniques, and Ellicott made many recommendations on the expedition's equipment and survey procedures that were later followed. The two men apparently got along well. When Simon Snyder followed McKean as governor of Pennsylvania, he fired Ellicott in 1809 due to political differences. A prominent supporter of Snyder was former General in Chief James Wilkinson, one of the four generals that Ellicott had denounced eleven years earlier and had come under a cloud of treason, along with Vice President Aaron Burr. Ellicott returned to private practice and was hired in February 1811 by David B. Mitchell, then governor of Georgia, to re-survey the border between Georgia and North Carolina to settle a border dispute between these two states. Although he started out in July, his expedition was delayed and had to work throughout the hard winter. Ellicott confirmed earlier findings that the border, which was supposed to follow latitude 35°N, was several miles further south than the Georgians claimed. His report was not well received by the Georgian administration, who furthermore refused to pay his fees. Ellicott returned in July 1812 to Pennsylvania. In 1813, Ellicott accepted a position as a professor for mathematics at the United States Military Academy at West Point, and the family left Lancaster and moved to West Point, New York. In 1817, Ellicott was again called upon to participate as astronomer in a field survey, namely a re-survey – agreed upon in the Treaty of Ghent – of the Collins–Valentine line. It was the last significant survey that he performed. Ellicott died three years later from a stroke in his home at West Point. In memoriam Andrew Ellicott Park at the West Cornerstone,