Robert Patterson was an Irish-American mathematician and director of the United States Mint from 1806 to 1824. He was a professor of mathematics at the University of Pennsylvania from 1779 to 1810, professor of natural history and mathematics and vice provost from 1810 to 1813. At the request of Thomas Jefferson, he advised Meriwether Lewis on the purchase and usage of navigational equipment for the Lewis and Clark Expedition.

The Lewis and Clark Expedition, also known as the Corps of Discovery Expedition, was the United States expedition to cross the newly acquired western portion of the country after the Louisiana Purchase. The Corps of Discovery was a select group of U.S. Army and civilian volunteers under the command of Captain Meriwether Lewis and his close friend Second Lieutenant William Clark. Clark, along with 30 others, set out from Camp Dubois, Illinois, on May 14, 1804, met Lewis and ten other members of the group in St. Charles, Missouri, then went up the Missouri River. The expedition crossed the Continental Divide of the Americas near the Lemhi Pass, eventually coming to the Columbia River, and the Pacific Ocean in 1805. The return voyage began on March 23, 1806, at Fort Clatsop, Oregon, ending six months later on September 23 of that year.