In 1789, at approximately 24 years old, he accompanied his brothers Andrew and Joseph Ellicott in 1789 to the British Province of Upper Canada in a survey to determine the western boundary of the State of New York.

[1] During 1791, 1792 and 1793, he assisted his brothers in the survey and mapping of the future City of Washington and in the survey of the original boundaries of the 100 square miles (260 km2) District of Columbia, which were established in the Boundary Markers of the Original District of Columbia.

[1][2] During November–December 1792, he led a survey that helped settle a boundary dispute within the present Ontario County in Western New York, which was resolved with the establishment of the Preemption Line.

[1][5] He was an unsuccessful candidate for election in 1820 to the Seventeenth Congress and succeeded by Nathaniel Allen.

[1][5] He then retired from active life, and in 1826 moved to Williamsville, New York, where he died December 10, 1827.