Andrew Ellicott (January 24, 1754 – August 28, 1820) was an American land surveyor who helped map many of the territories west of the Appalachians, surveyed the boundaries of the District of Columbia, continued and completed Pierre (Peter) Charles L'Enfant's work on the plan for Washington, D.C., and served as a teacher in survey methods for Meriwether Lewis. Early life Andrew Ellicott was born in Buckingham Township, Bucks County, Pennsylvania as the first of nine children of Joseph Ellicott (1732–1780) and his wife Judith (née Blaker or Bleaker, 1729–1809). The Quaker family lived in modest conditions; his father was a miller and clockmaker. Young Andrew was educated at the local Quaker school, where Robert Patterson, who later became a professor and vice provost at the University of Pennsylvania in Philadelphia, was his teacher for some time. Andrew was a talented mechanic like many of the family and showed some mathematical talent, too. In 1770, his father, together with his uncles Andrew and John, purchased land on the falls of the Patapsco River, upriver and west of Baltimore and the Chesapeake Bay. There they set up a new milling business, founding the town of Ellicott's Mills in 1772 (today's Ellicott City, Maryland). Three years later, Andrew married Sarah Brown (1756/8–1827) of Newtown, Pennsylvania, with whom he would have ten children, one of which died as a child. When the Revolutionary War broke out in 1775, Andrew enlisted as a commissioned officer in the Elk Ridge Battalion of the newly organized Maryland state militia despite his Quaker upbringing. During the course of the war, he rose to the rank of major, a title he would keep as an honorific throughout his life. Survey work After the war, Ellicott returned home to Ellicott's Mills until he was appointed, in 1784, a member of the survey group tasked with extending the survey of the Mason-Dixon line for the borders between Pennsylvania / Delaware with Maryland that had been abandoned in 1767 and then been stalled during the war. In this survey, he worked alongside David Rittenhouse and Bishop James Madison, making first connections with the scientific society of Philadelphia. Following the death of their second son, the Ellicotts moved to Baltimore in 1785, where Andrew taught mathematics at the Baltimore Academy and was even elected to the Maryland General Assembly (state legislature) in 1786. The same year, he was called upon for a survey