If you grew up in the United States, you probably learned the United States Customary System (USCS) for weights and measures. USCS terms like inches, feet, pounds, and miles are derived from the British Imperial System, steeped in a long history of application and use. Any introduction to the metric system may have muddied the measurement waters, adding unfamiliar words and awkward conversions to your school day.
While Americans continue to use the USCS, most of the world has shifted to the metric system. The metric system, or International System of Units (SI), was introduced in France during the late 18th century and includes seven foundational units of measurement, the most common of which include meters and kilograms. SI has, according to its proponents, more utility and universality than other systems, making it the preferred system for weights and measures across the globe.
If this is true, why does the United States remain one of the few countries not to use the metric system as its primary system of measurement? The reasons Americans don't use the metric system are complicated, combining political and economic considerations with nationalist pride, but if you look closely, you can see the influence of SI in the United States. Whether or not this will eventually come full-scale remains to be seen, but here's what has shaped the use of the metric system in the United States so far.
The Metric System Was Too New And Too French For Early Americans, Even Francophile Thomas Jefferson
As early as the 1770s, Thomas Jefferson expressed the need for the United States to establish coinage based on the decimal system, part of his overall belief in the importance of a uniform system of weights and measures. Jefferson had developed a decimal system of measurement, echoing the efforts of men like Simon Stevin in Flanders in 1585 and Englishman John Wilkins in 1668.
When Jefferson was in France during the 1780s, he had long conversations about such standardized systems, notably exchanging ideas with statesman and cleric Charles Maurice de Talleyrand-Perigord. Often referred to simply as Talleyrand, the French bishop would go on to be the force behind the adoption of a standardized system of measurement by the French Assembly in 1790.
What France implemented during the 1790s was based on natural phenomena instead of the traditional seconds pendulum technique. For the French, the fundamental measure - or metre (from the Greek word "metron," for measure) - was set at 1/10,000,000 the length of a meridian line from the equator to the North Pole. Using the line that went through Paris, the system of measurement was decidedly French.
Jefferson wasn't opposed to using a comparable system, but advocated for the continued use of a seconds pendulum - a rod that swung back and forth in two seconds - to determine the length of a meter. Jefferson also took issue with the system that seemed to apply only to France.
George Washington Proposed A Standard US System Of Weights And Measures, But Congress Didn’t Follow Through To Develop One
In 1790, President George Washington told Congress, "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 Washington's speech, representatives attempted to establish a committee on the topic but the task ultimately fell into the hands of Secretary of State Thomas Jefferson. Already actively working on a solution, Jefferson submitted a report to Congress during the summer of 1790. The report included two potential plans, neither of which received consideration by the legislative body.
In December 1790, Washington reemphasized the importance of the uniformity of weights and measures in a statement to Congress, prompting the Senate to consider Jefferson's report. Again, nothing moved forward and, in October 1791, Washington reminded Congress, "A uniformity in the weights and measures of the country is among the important objects submitted to you by the Constitution..."
Debates and discussions about establishing a uniform system slogged on through mid-1796, at which point a designated committee attempted to address concerns about how to take appropriate measurements. It recommended, "The President of the United States... employ such persons of sufficient mathematic skill" to carry out Jefferson's plan to use a seconds pendulum to determine the length of a meter. After multiple readings of the report, however, any move toward establishing an official system was again deferred.
British Pirates Prevented A French Botanist From Reaching The US To Promote The Metric System
Joseph Dombey was a trained physician and naturalist working at the Jardin du Roi - Royal Gardens - in Paris during the 1770s. As part of an expedition with Spanish colleagues in 1777, Dombey visited Peru and familiarized himself with plants he could take back to Europe.
After returning to France in 1788, Dombey entered into correspondence with Thomas Jefferson. Exchanges between the men reflected the mutual benefits they would receive if Dombey were to visit North America, with Dombey requesting to botanize for "for two to three years" while simultaneously bringing Jefferson prototypes of newly determined metric measurements.
Dombey boarded a ship, the Soon, for North America in April 1794, but he never arrived at his destination. A storm detoured the vessel to the Caribbean, where British privateers bombarded and raided it. Dombey was taken captive and held on the small island of Montserrat, where he perished soon after. Dombey's metric prototypes - one demonstrative of the length of a meter and the other, called a "grave," representing the weight of a kilogram - were sold off by the pirates, never reaching the awaiting Jefferson.
Both items were later acquired by the French minister in the United States, Joseph Fauchet, who passed them along to then-Secretary of State Edmund Randolph in 1795. In the words of historian Andro Linklater in his work, Measuring America, both Fauchet and Randolph "failed to appreciate the significance of the two standards. Indeed the prototypes of the meter and the kilogram were never shown to Congress at all."
During The Industrial Revolution, US Companies Said It Was Too Expensive To Convert
Despite the acknowledgement by Secretary of State John Quincy Adams in 1821 that the French system had its merits, the general sentiment in the US was, in Adams's opinion:
The final prevalence of this system beyond the boundaries of France's power must await the time when the example of its benefits, long and practically enjoyed, shall acquire the ascendancy over the opinions of other nations which gives motion to the spring and direction to the wheels of power.
As a result, repeated calls for uniformity never came to fruition. Manufacturers in the United States fitted their factories with machines and equipment based on British precedents, but they often varied by state and resulted in widespread variability and inconsistency. In 1832, the government formally adopted measurements that resembled those used in Great Britain, specifically the yard, gallon, and bushel, a moderate move toward consistency.
By the end of the 19th century, these US customary units became so ingrained in US practices and processes that major industrialists argued switching to the metric system would be too costly, inconvenient, and unrealistic. Even after Congress passed an act legalizing the use of metric weights and measures in 1866, the anti-metric lobby remained strong. As late as 1921, the International Institute for Preserving and Perfecting (the Anglo-Saxon) Weights and Measures broke down the economic consequences:
(1) ...the cost to each artisan would be at least $2.50 (for masons and blacksmiths) and could go as high as $32.60 (for tool makers); (2) that the cost to each household of replacing common measuring tools would range from $2.90 to $10.75, and that, with 28 million households in the country the minimum cost would be $81.2 million; (3) that the bill would impose hardships on the farmer by destroying ingrained relationships built up over time (such as price per bushel or per pound) and forcing him to use a mixture of two systems; (4) that the railroads would have to change all freight and passenger tariffs, entailing great expense and causing confusion; and (5) that the cost to manufacturing firms alone would be astronomical if an Institute survey of 31 firms, which had yielded an average cost of $715,489 per firm, was any indication.