Historical Markers
Robert Patterson (1743 -1824) Historical Marker
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Robert Patterson (1743 -1824)

Philadelphia and its Countryside/Lehigh Valley


Marker Location:
West side of 9th St., south of Market St., Philadelphia

Dedication Date:
July 22, 2004

Behind the Marker

A watercolor portrait of Robert Patterson
Robert Patterson
After learning the art of map making with markerAndrew Ellicott in Lancaster, Pennsylvania, markerMeriwether Lewis in May 1803 took the stage road to Philadelphia to continue his studies and to shop for supplies and equipment for his cross-continental expedition. To further hone his navigation and mapping skills, Clark visited Ellicott's former teacher, University of Pennsylvania professor of mathematics Robert Patterson.

Born in 1743 in Hillsborough, County Down, Ireland, Robert Patterson had grown up in the crushing poverty of the Irish countryside. Early on, Patterson showed an aptitude for numbers. On clear nights, he would find inspiration in the skies, a fascination that would later inspire his development of an important, new method of navigation based on the calculation of latitude through the use of lunar observations.
Page from Meriwether Lewis Astronomy Notebook, c. 1803-1805
Page from Meriwether Lewis' Astronomy Notebook, c. 1803 -1805

Nearly destitute as a young man, Patterson sailed into the port of Philadelphia in 1768, determined to earn enough money to bring his family to America. He was confident that his mathematical gifts would help him find work, and he was right. Philadelphia offered Patterson, like other talented immigrants, opportunities unavailable in eighteenth-century Ireland. Within a week of his arrival, Patterson became a schoolmaster in Buckingham, Bucks County.

In 1774, he assumed the position of principal at the Wilmington Academy in Delaware. While these positions may have permitted Patterson to use his gifts for numbers and teaching -and allow him to save enough money to pay for his family's journey to America - they did not allow him to exercise his exceptional mathematical skills or understanding of astronomy. In 1779, Patterson returned to Philadelphia to accept a professorship in Mathematics and Natural Philosophy at the University of Pennsylvania.

Under Patterson's guidance, Lewis learned more about the mapmaking skills and instruments he had studied with Ellicott in Lancaster. At Jefferson's request, Patterson also helped Lewis purchase the right instruments for the expedition. This way Lewis could also train with the very same instruments he would use on the unknown rugged rivers, mountains, and trails of the west.
The travels of Capts. Lewis and Clark: Map of the Country Inhabited by the Western Tribes of Indians
"Map of the Country Inhabited by the Western Tribes of Indians," in...

Patterson provided a valuable second opinion about the surveying system that Lewis should use on the Expedition. He agreed with Ellicott that Lewis should not depend on a theodolite for calculating latitude - the fragile measuring instrument that Jefferson had suggested. Arguing that the theodolite "would be very liable to get out of order" and "would be liable to many objections," the two men insisted that Lewis should use a sextant, an accurate and rugged optical device, invented in 1731, for the measurement of latitude.

On the advice that they were "indispensably necessary," Lewis purchased two sextants, as well as "an artificial horizon or two, a good Arnold's watch or chronometer, a surveyor's compass with a ball and socket and two pole chains, and a set of plotting instruments." Lewis bought the chronometer at Thomas Parker's shop on South 3rd Street for $250, the largest sum paid for any single item taken on the Expedition.

The time that Lewis spent with Ellicott and Patterson proved invaluable to the success of the Expedition. When finally published in 1814, The History of the Expedition Under the Command of Captains Lewis and Clark included the first detailed map of the American West - a map made possible by the training and instruments that Meriwether Lewis had acquired in southeastern Pennsylvania.

Robert Patterson remained at the University of Pennsylvania until his retirement in 1814. In 1805, Jefferson appointed him to a directorship at the United States Mint, a position he held until his death in 1824.
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