In 1811 Ellicott became commissioner to represent Georgia in locating the Georgia-North Carolina boundary, a project on which he was engaged for the major part of the following year.
In 1815 President Madison appointed Ellicott professor of mathematics at West Point, with the rank of major. This is an appointment he kept until his death in 1820. It was interrupted in 1817 when the Government required his services as astronomer to locate a portion of the United States-Canadian boundary in accordance with the fifth article of the Treaty of Ghent.
Figure 10.—Transit and equal-altitude instrument (left) made by Ellicott in 1789 and used by him in the survey of the boundary between the United States and Florida and in other surveys. USNM 152080.
Figure 11.—Zenith sector with focal length of 6 ft., made by David Rittenhouse and revised by Andrew Ellicott. Described in Journal of Andrew Ellicott (Philadelphia, 1803). USNM 152078.
Ellicott was a member of a number of learned societies, including the American Philosophical Society, the Society for the Promotion of Useful Arts of Albany, and of the National Institute of France.
Ellicott constructed a number of instruments for surveying and astronomical observation, and he designed and used others that were produced by his friend David Rittenhouse[10] (see figs. 10, 11). Of particular interest in connection with Ellicott's career as a clockmaker and instrument maker are two advertisements that appeared in the Baltimore newspapers. The first one was in the Maryland Journal and Baltimore Daily Advertiser on April 7, 1778:
Ellicott's Upper Mills, April 4, 1778. Wanted, a person acquainted with the Clock-Making business, and able to work by directions. Such a person will meet with good encouragement by applying to Andrew Ellicott, sen.
The second advertisement, in the same vein, appeared in the May 16, 1780, issue of the Maryland Journal:
Good Encouragement will be given to either Clock or Mathematical instrument makers, by the subscriber, living in Baltimore-Town. Andrew Ellicott.