In his travels to and from France as a diplomat, Benjamin Franklin (1706–1790) noticed a difference in speed in the two directions of travel between France and America. He was the first to study ships’ reports seriously to determine the cause of the speed variation. As a result, he found that there was a current of warm water coming from the Gulf of Mexico that crossed the North Atlantic Ocean in the direction of Europe. In 1770, Franklin mapped it.

Franklin thought the current started in the Gulf of Mexico. However, the Gulf Stream actually originates in the western Caribbean Sea and moves through the Gulf of Mexico, the Straits of Florida, then north along the east coast of the United States to Cape Hatteras in North Carolina, where it becomes northeast. The Gulf Stream eventually breaks up near Newfoundland, Canada, to form smaller currents or eddies. Some of these eddies blow toward the British Isles and Norway, causing the climate of these regions to be milder than other areas of northwestern Europe.