ERSKINE, ROBERT. (1735–1780). Mapmaker of the Continental army. A native of Scotland, after studying at the University of Edinburgh he went to London, where the treachery of a business partner got him seriously in debt. Escaping a jail sentence because of his excellent character and innocence in the affair, he continued his studies, and for his work in the field of hydraulic engineering he became a fellow of the Royal Society (F.R.S.) in 1771. He reached New York City on 5 June 1771 as the representative of a British capitalist who had invested in the American Iron Company, which was mining and manufacturing at Ringwood in the upper part of Passaic County, New Jersey. He soon became a supporter of the Patriot cause and in the summer of 1775 organized his employees into a military company. Erskine was made a captain in the Bergen County militia, and his men were exempted from compulsory service in other units.
Washington met Erskine early in the war and, learning that this able engineer and F.R.S. was well acquainted with the region west of the Hudson, offered him the position of "geographer and surveyor-general to the Continental Army." On 27 July 1777 Erskine was commissioned "Geographer and Surveyor to the Army of the United States."
In three years of zealous work, Erskine produced maps that contributed significantly to Washington's operations, despite their numerous inconsistencies in scale and errors in distance and orientation. Among the prized possessions of the Pierpont Morgan Library in New York City is an engraved copy, with annotations believed to be in Washington's hand, of "A Map of part of the States of New-York and New-Jersey: Laid down, chiefly from Actual Surveys, received from the Right Honble Ld Stirling and others, and Deliniated for the use of His Excely Genl. Washington, by Robt. Erskine F.R.S. 1777."
During the war, Erskine's iron works factory at Ringwood manufactured items used by the American army. He also designed and produced the chevaux-de-frise (chains) that were placed in the Hudson River to deter passage of British ships.
Erskine died on 2 October 1780 of a respiratory illness contracted during his fieldwork. In his military journal entry for 25 January 1781, Dr. James Thacher, who was accompanying General Robert Howe's force from the Hudson Highlands to put down the mutiny of the New Jersey Line, wrote of the excellent accommodations given to Howe and his field officers in Pompton "at the house of Mrs. Erskine, the amiable widow of the late respectable geographer of our army."
Erskine's papers are held by the New Jersey Historical Society. Records of the quartermaster general contain numerous references to Erskine and his works. His original maps are in the possession of the New York Historical Society Library.
Harley, John B., Barbara B. Petchenik, and Lawrence W. Towner. Mapping the American Revolutionary War. Chicago: University of Chicago Press, 1978.
revised by Harry M. Ward