An oft-repeated "weird fact" is the claim that, if not for the scourge of Caribbean piracy, the United States would have adopted the metric system in the 1790s, making it the country's standard system of measurement, instead of what is now known as the U.S. customary units.
The argument, as described in a 2017 Washington Post article, centers around French scientist Joseph Dombey, who had been enlisted to deliver by ship a pair of the world's only kilogram and meter standards to then-U.S. Secretary of State Thomas Jefferson:
In 1793, botanist and aristocrat Joseph Dombey set sail from Paris with two standards for the new "metric system": a rod that measured exactly a meter, and a copper cylinder called a "grave" that weighed precisely one kilogram. He was journeying all the way across the Atlantic to meet Secretary of State Thomas Jefferson — a fellow fan of base-ten systems who, Dombey hoped, would help persuade Congress to go metric.
According to the claim, the ship was looted by pirates, who killed Dombey, and the rod and grave disappeared; as a result, Jefferson was robbed of the chance to mull the metric system for the U.S.:
Had Dombey made it to the United States on schedule, he and Jefferson may have talked Congress into caring about how we measure distance and mass. This country could have gone metric right from the beginning, instead of being dragged into the system kicking and screaming.
This tale about Dombey, the objects in his possession while aboard the ship, and his tragic death while held as a prisoner of British privateers was factual. However, the conclusion that this event in 1793 had any bearing on the U.S.'s failure to adopt the metric system was false, considering historical context.
Firstly, Jefferson did not need to be convinced that a standardized, decimal-based system had benefits. Before Dombey's ship journey, in 1790, Jefferson had already published and submitted to Congress his most significant work on the topic of uniform measurements. It wasn't until the 1820s that any legislative progress toward a U.S., unified measurement system began.
The decades of legislative stalemate between Jefferson's report and the establishment of a standardized system was not caused by a lack of access to metric standards or visual aids — i.e., items on Dombey's ship — and would have persisted had Dombey arrived intact.
What Measurement System Did First Americans Use?
At the time of the American Revolution, the 13 colonies, by and large, used a presently defunct English measuring system with units of measurement — ounces, pounds, feet, miles, etc. — that sound familiar to America's present system. There were regional differences and exceptions to that general rule. Dutch measuring systems were used in much of New York, for example. Also, some units were not defined the same across colonies. These factors made interstate and foreign trade challenging.
The importance of a unified and standardized system had been a concern during the Continental Congresses that preceded and directly followed the American Revolution. The power to define and establish such a system was ultimately bestowed on Congress with the ratification of the U.S. Constitution.
During his first inaugural address as president, George Washington reminded the newly formed Congress of this obligation, stating that, "Uniformity in the Currency, Weights and Measures of the United States is an object of great importance, and will, I am persuaded, be duly attended to."
In response to that call, members of Congress created a series of congressional committees based on Washington's directives. Ultimately, Congress proposed to make the secretary of state — that is, Jefferson — draft a "plan or plans" for enacting such a system.
Meanwhile, within the scientific community internationally, scholars were calling for a unified measurement standard across all nations, using units of 10. That system, they argued, would make measurements and conversions easy for the general population.
Jefferson Proposed Two Options to Congress
In Jefferson's report to Congress, delivered on July 4, 1790, he laid out two potential plans. The first assumed that "present measures and weights are to be retained, but to be rendered uniform and invariable, by bringing them to the same invariable standard." Jefferson proposed a standard based on a pendulum with oscillations that were exactly one second in length.
Jefferson's second plan used the same standard but involved recreating U.S. measurement units with a decimalized system in which every unit contained 10 units of a smaller unit. (That proposal was similar to the metric system that France was simultaneously developing.) While a decimalized system had already been proposed for currency in the U.S., Jefferson floated this idea for units of measurement, as well. He said to the House of Representatives:
Is it in contemplation with the House of Representatives to extend a like improvement to our measures and weights, and to arrange them also in a decimal ratio? The facility which this would introduce into the vulgar arithmetic would unquestionably be soon and sensibly felt by the whole mass of the people, who would thereby be enabled to compute for themselves whatever they should have occasion to buy, to sell, or to measure, which the present complicated and difficult ratios place beyond their computation for the most part.
While Jefferson proposed both plans to Congress, documentation shows his heart always lay in adopting the decimalized system (the second option). He advocated for such a system until his death, according to the National Archives:
The resolution of the House of Representatives called upon the Secretary of State to prepare "a plan or plans," but in its formative state Jefferson's report called for a single, integrated system of weights, measures, and coins based on decimal calculation and employing the second's pendulum as the standard of length and the cubic inch of distilled water as the standard of weight. [...] This was essentially the plan that Jefferson had had in mind in 1784 and continued with characteristic persistence and patience to urge upon the nation until the end of his life.
Jefferson's report is widely considered by historians to be a foundational and important document in the history of unit standardization in America. That said, it did not lead to any policy, nor did it spur legislation. The report was essentially filed away for a later Congress to deal with.
What Happened to Dombey?
In 1793 — well after Jefferson's report to Congress — Dombey, the French botanist, wrote to Jefferson, telling him he would be in America in the coming year as part of a scientific expedition. Through conversation with luminaries in France, the French agreed to send with Dombey an official kilogram and meter standard — that is, the rod and grave — for the country's newly developed metric system to give to Jefferson.
As Jefferson later learned through correspondence with others, Dombey never made it to the U.S — he was killed while making the journey. Jefferson was informed of this news in a letter from a New York merchant, Joseph L'Epine, in 1794, which said Dombey's death was at the hands of British privateers, or British pirates operating with the tacit approval of the King of England:
I am most mortified that The Event of Mr. Joseph Dombey's death is the First occasion which gives me the honor of writing to you. My Brig […] left last January, from the haven of Grace to go here; having as Passenger Mr. Jh. Dombey. [...] On February 12 last, this Brig Received such a terrible Gale, that he made Sail (having a Waterway) for the first port he could find, and He made his Release in distress at Guadeloupe, where He had the said Brig repaired to Continue his Voyage without his ballast. [...]
Mr. Dombey, though ill, re-embarked; but they had the Misfortune to be Arrested by an English Corsair on the 1st. last April, which took them to Montserrat; and the Brigands of the said corsair pillaged and treated Mr. Dombey and Mr. Bacchus so badly that they contributed much to their death.
It is unclear what happened to the items in Dombey's charge. In later correspondence to the French count of Volney in 1796, Jefferson expressed his regret at the fate of Dombey and inquired about the metric standards that had been in his charge:
Certainly it would be a great gratification to me to receive the Mètre and Grave committed to Mr. Dombey for me, and that you would be so good as to be the channel of my acknowledgements to Bishop Gregoire or any one else to whom I should owe this favor.
After serving as secretary of state, Jefferson served as president between 1801 and 1809 — a period in which no progress was made toward adopting any of his ideas regarding standard units of measurement. As president, he did not raise the issue formally, but historical records show he advocated for a standardized decimal-based system until his death.
The Reality: Congressional Stalemate
"The Dombey event is probably a bit of a footnote to history," said historian Keith Martin, of the National Institute of Standards and Technology, in the 2017 Washington Post story highlighting the affair.
Indeed, the fact that the early U.S. did not adopt standardized measurements was not due to a lack of physical standard to inspire people.
The problem with moving forward on any plan, according to the National Archives, was congressional inaction and a confusing mix of competing proposals. Despite repeated instructions by Washington and several later presidents to get the job done, nothing actionable was signed into law until the 1820s and '30s. As reported in a history of early congressional action on the issue written by the U.S Department of Commerce:
The first act of Congress to be put into effect promptly after passage was the Mint Act of 1828 adopting the troy pound and providing for uniformity in the weight of the coins of the United States. After the passage of this act, the work of securing uniformity in weights and measures was seriously begun. This work finally resulted in the construction and adoption of standards as provided in the joint resolutions of 1836 and 1838.
The resolutions in 1836 and 1838 called for the creation of locally produced pound standards that would be distributed to custom houses at maritime ports, beginning the slow road to reform that ultimately led to our current system.
While it was true that physical items to demonstrate metric standards intended for Jefferson did not make it to him because of piracy, there was no plausible alternative history in which the delivery of such items would have overcome the political stalemate over establishing a standardized measuring system — no matter if it was the decimal-based metric system or something else.
At the time of Dombey's death, Jefferson was already convinced of the virtue of these ideas. Congress was not. As such, we rate the claim that piracy prevented the U.S. adoption of the metric system as "False."