From Taking Measure, a blog of the National Institute of Standards and Technology (via Slate Star Codex), an interesting historical anecdote offering a reason why the United States did not adopt the metric system.

Pirates of the Caribbean (Metric Edition)

September 19, 2017
by Keith Martin

To save his own life, Joseph Dombey had an idea. As two pirate ships surrounded the ship he was on in the Caribbean Sea in 1794, Dombey scrambled below deck, disrobing as he went. He appropriated the outfit of one of the ship’s many Spanish sailors and prayed that he had picked up enough of their language during his trips to South America to blend in. Dombey shouldn’t have been in this position. In fact, he shouldn’t have been in the Caribbean at all. None other than Thomas Jefferson himself was expecting to meet with Dombey in Philadelphia at that very moment.

Dombey’s fate that day arguably delayed the adoption of the metric system in the United States by almost a century and left us as one of the few countries in the world still using non-metric units for our everyday measurements.The marauders now swarming Dombey’s ship were a particular breed of pirate: British privateers— the state-sponsored terrorists of the 18th century. These waterborne gangs had the tacit approval of the government in London to harass and plunder other countries’ maritime commerce and keep part of the spoils as their profit.

After seizing control of the ship, the pirates came across a sailor speaking Spanish with a curiously French accent—Joseph Dombey. A French physician and botanist acting under orders from the French government, Dombey had left the port city of Le Havre, France, weeks earlier for Philadelphia and the meeting with Jefferson, the United States’ first secretary of state and future president. But storms had pushed Dombey’s ship off course and deep into pirate territory.

France had supported the United States against the British in the War of Independence, and now they intended to build closer economic ties with the new American nation. Dombey was to negotiate with Jefferson for grain exports to France and to deliver two new French measurement standards: a standard of length (the meter) and a standard of mass called, rather ominously, a grave, to be considered by the U.S. for adoption. (The grave would be renamed the kilogram a year later in 1795.)

In many ways, Dombey was an excellent choice for this mission. Having already been on several trips to South America to collect botanical specimens, he was an experienced trans-Atlantic traveler. His knowledge of plants would also be of help in his agricultural trade negotiations with Jefferson. And Dombey’s scientific training as a physician and botanist gave him an understanding of the importance of accurate weights and measures, so it was highly likely that he would be able to convince Congress to adopt the new French standards, which would later come to be known as the metric system.

Despite his qualifications, Dombey lacked one important attribute: luck. His previous trips had all ended in failure. He had spent two years in Peru collecting plants that could be usefully cultivated in France, only to have the shipment captured by the British. A second collecting trip, this time in Chile and in collaboration with Spain, fell apart over a business dispute, with Spain keeping all the valuable specimens. But Dombey’s voyage to Philadelphia would turn out to be his most disastrous.

Upon learning his true identity, the pirates imprisoned Dombey on the Caribbean island of Montserrat. Unfortunately, Dombey died before they were able to ransom him to the French, and the units of measure in his charge never made it into Jefferson’s hands.

Some historians view this event as a tragic missed opportunity whose consequences we are still living with today. When the U.S. became an independent nation, it inherited an inconsistent collection of traditional British weights and measures. Congress was aware of the flaws with its British measures, and a congressional committee was formed to recommend solutions. Thomas Jefferson, an admirer of French scientific ideas, lobbied for a measurement system similar to that of France. But Congress didn’t adopt it, and the British-influenced system took hold in the U.S. instead. However, If pirates hadn’t intercepted Dombey on his way to Philadelphia, the situation might be very different today.

More at the link.