A survey of New York's Westchester County and vicinity, circa 1778, by Robert Erskine
and Simeon DeWitt, who would eventually succeed Erskine as Surveyor General.

A map of Morristown, New Jersey by Robert Erskine, 1779. General Washington and
his troops returned to Morristown repeatedly over the course of the Revolutionary War,
earning the hamlet the nickname “the military capitol of the American Revolution.

Two years into the Revolutionary War, General George Washington became convinced the Army’s limited ability to produce accurate topographical maps was a major handicap. In 1777, Washington appointed Scotsman Robert Erskine the Army’s chief cartographer. Born in 1735, Erskine settled in colonial New Jersey. He would soon form his own militia in support of the American Revolutionary cause and serve as an officer in the Continental Army. As the war progressed, General George Washington sought tactical advantage in the form of a gentleman of “known character and probity [who] could be employed in making maps from actual surveys of roads, rivers, bridges and fords over them, the mountains and passes through them.” Washington was impressed by Erskine’s engineering experience and prodigious knowledge of New York’s Hudson River Valley. He appointed the young man to the newly formed post of Geographer and Surveyor General of the Continental Army.

Surveyors and mapmakers of the era had little technology to rely upon—in many instances there weren’t even roads—forcing them to traverse unfamiliar territory and collect data on foot. More than one person was needed to create a faithful map. For his team, Erskine required “six attendants to each surveyor, […] two chain-bearers, one to carry the instrument, and three to hold the flagstaffs. [...] From what one surveyor can do, it will therefore appear that in making a plan, like all other business, the more hands are employed in it, the sooner it may be accomplished.

Robert Erskine passed away suddenly in October 1780. His legacy lived on in the form of more than 275 maps he produced under the auspices of the Continental Army—many still hold historical value for scholars today. He is also credited with advancing the field of hydraulics, inventing a “Continual Steam Pump,” the “Platometer” measuring tool, and a centrifugal hydraulic engine.