Who first charted the Gulf Stream?

Benjamin Franklin was the first person to chart the Gulf Stream.

Ben Franklin's map of the Gulf Stream

Alexander Agassiz, a preeminent oceanographer of the 19th century, attributed the first scientific basis for exploring the Gulf Stream to American statesman Benjamin Franklin.  Franklin published this map of the Gulf Stream in 1769, 200 years before a submersible named after him drifted below the surface to study this river in the ocean.

Although first observed in 1513 by Ponce de Leon, the Gulf Stream was not charted until the early 1770s by Benjamin Franklin, with the help of a Nantucket sea captain.

Around 1770, the Board of Customs in Boston, Massachusetts, noticed that packets travelling between Falmouth, Massachusetts, and New York, New York, by sea took two weeks longer to arrive than merchants travelling from London to Rhode Island. This was perplexing as Falmouth and New York were less than a day apart by road.

Franklin spoke with a sea captain who told him that while fishing for whales, he noticed that the whales would swim alongside the Gulf Stream, but never in it. Fishermen would frequently cross the Gulf Stream, where they passed packet ships sailing within, against the current. This was the reason for the delays. Franklin had the captain mark the location of the Gulf Stream, as well as the directions of its currents.

In 1843, the United States Coast Survey, NOAA’s earliest “ancestor”, set out to study the Gulf Stream in more detail. They wanted to determine the depth of the water, the temperature of the water at different depths, the characteristics of the ocean bottom, the direction and velocity of the currents at different depths, and the extent of plant and animal life. Their early observations led them to discover features such as cool and warm water banding, as well as the “Charleston Bump.”