This article records tradition as it has been passed down and reported. Its sources are not yet part of the atlas's verified catalogue.
Benjamin Franklin, serving as a colonial postal official in the 1760s, became curious about a specific practical mystery: British packet ships carrying mail from England to the American colonies routinely took two weeks longer to make the crossing than ordinary merchant ships sailing the same general route, despite the mail ships supposedly being faster vessels. Franklin's cousin, Timothy Folger, a Nantucket whaling ship captain, had a ready explanation. Whalers, who spent long stretches tracking their prey across the Atlantic, had long since learned to recognize a warm, fast-moving current running against a westbound ship and to steer around it, while the British packet captains, unaware of the current's exact path, sailed straight through it, fighting a current running directly against them the entire way.
Franklin and Folger worked together to chart the current's path in 1769, producing what is generally regarded as the first systematic map of the Gulf Stream, based on temperature readings, water color observations and the accumulated sailing experience of Nantucket's whaling captains rather than on any theory of ocean circulation, since the physical mechanisms driving the current, wind, the Coriolis effect and basin geography, would not be understood in any real detail for more than a century afterward. Franklin published the chart to help British ships avoid the current on the westbound crossing and use it to advantage heading east, a practical navigational fix built entirely from empirical observation.
Modern tracking of the Gulf Stream and currents like it bears almost no resemblance to Franklin's method beyond the basic goal of knowing where the water is moving and how fast. Satellite altimetry, measuring tiny variations in sea surface height that reveal a current's location and strength from orbit, combined with drifting buoys and autonomous underwater gliders, now lets oceanographers track the Gulf Stream's position and strength continuously rather than reconstructing it after the fact from a captain's logbook. That continuous tracking has taken on a significance Franklin could not have anticipated: some climate models project that a warming climate could weaken the Atlantic's deep overturning circulation, the same broader current system the Gulf Stream is part of, and monitoring its strength in something close to real time has become a genuine, actively studied question in climate science rather than only a matter of shipping schedules.