Why Didn’t the US Adopt the Metric System Long Ago?

Why hasn’t the United States adopted the metric system for widespread use? I’ve generally thought there were two reasons. One is that with the enormous US internal market, there was less incentive to follow international measurement standards. The other was that the US has long had a brash and rebellious streak, a “you’re not the boss of me” vibe, which means that there will inevitably be pushback against some external measurement system invented by a French guy and run an international committee based in a Paris suburb.

However, Stephen Mihm makes a persuasive case that my internal monologue about the metric system is wrong, or at least seriously incomplete, in “Inching toward Modernity: Industrial Standards and the Fate of the Metric System in the United States” (Business History Review, Spring 2022, pp. 47-76, needs a library subscription to access). Mihm focuses on the early battles over US adoption of the metric system, waged in the 19th and early 20th century. He makes the case that the metric system was in fact blocked by university-trained engineers and management, with the support of big manufacturing firms.

The metric system is part of US policy discussions in the early 1800s, after it is adopted in France. Mihm writes:

By the 1810s, most commentators considered the metric system a failed experiment. One writer in 1813 noted that the French government, despite wielding considerably more power over their own populace than the United States could, nonetheless failed to secure adoption of the metric units. “The new measures . . . are on the counter . . . but the transactions are regulated by the old.” In 1819, a House of Representatives committee studying the issue concurred in this assessment, pointing to France’s failure to secure widespread adoption of the metric system.

Throughout the 19th century, there was an ongoing discussion about appropriate systems of weights and measures, and the metric system was part of those discussions. But the battle-lines for this dispute began to be clarified in 1860s. The growth of industrialization across the United States meant that there was also a movement across US industries and engineers to standardize measurements in areas like screw threads, nuts and bolts, sheet metal, wire, and pipe–so that it was possible for a manufacturing firm to use inputs from a variety of different suppliers around the country. confident that the parts would fit together. A similar movement arose in the railroad industry, standardizing axles, couplings, valves, and other elements so that rolling stock would fit together. This movement was led by a mixture of mechanical engineers and management experts, and it was based on the inch as the standard unit of measure. At least at this time, it’s fair to say that most people cared much less about measures of weight or volume.

But a number of scientists and social reformers preferred the logical organization of the metric system. Mihm reports that in 1863, “the newly created National Academy of Sciences recommended that the United States adopt the metric system. That same year, the United States participated in international congresses on postage and statistics that endorsed the metric system for both scientific and commercial purposes.” Federal legislation passed in 1866 to legalize the use of the metric system.

The struggle over how the US measuring system would be standardized then evolves from the late 1800s up through the early 20th century. Mihm lays out the details. For example, in 1873 the prominent educator and president of Columbia University, Frederick Barnard, founded the the American Metrological Society to push for the metric system. In 1874, a American Railway Master Mechanics’ Association instead pushed for the already-developed system of standardization based on inches. He said: “While French savants were laboring to build up this decimal system of interchangeable measures … the better class of American mechanics were solving the problem of making machinery with interchangeable parts.”

The dispute got a little weird at times. Mihm tells of the International Institute for Preserving and Protecting Weights and Measures, founded in 1879, which promoted “Great Pyramid metrology,” defined as “a belief that the Egyptians had inscribed the inch as a sacred unit of measurement in the design of their famed structures. … Over the 1870s and 1880s, pyramid metrology channeled much of the opposition to the metric system in the United States.” Lest this seem a little whacky to us, remember that this is a time when scientists and engineers were also exploring mesmerism and divining rods. To put it another way, being a logically rigorous scientist or engineer in one area does not rule out more imaginative approaches to other topics, then or now.

The central practical issue became what economists call “path-dependency.” Imagine two different paths for standardization. Perhaps in the abstract one is preferable. But if you have already committed to the other path, and all your machine tools and existing equipment are based on that alternative path, and all your workers and suppliers and customers are using that other path–then the costs of transition to the other approach are formidable. Indeed, the longer you wait to make the switch, the more committed you are to the path you are on. For example, if you have laid down pipelines for water and oil measured in an inch-based system, as well as set up train tracks and rolling stock based on that system, then you are going to have physical equipment for an inch-based system around for decades.

The metric issue kept bubbling along. “In 1896, the House of Representatives considered a bill that mandated the immediate, exclusive use of the metric system in the federal government, with the rest of the country to follow suit a few years later.” It almost passed, with relatively little attention, but was concern that the risk of disrupting industrial production in an election year wasn’t a political winner. When the US Bureau of Standards was created in 1901, the administrators preferred the metric system, but engineers and big companies pushed back hard.

By the early 20th century, remember that this argument had now been going on for decades. US industry had already felt firmly committed to an inch-based system of measurement back in the 1860s and 1870s; by the early 1900s, the idea of redoing all of their capital stock in the metric system seemed crazy to them. Indeed, US manufacturing was so dominant in the world at this time that US companies routinely exported inch-based equipment to companies in countries that were nominally on the metric system already. Some US manufacturers even argued that the unique inch-based measurement system helped to protect them from foreign competitors.

Bills for the metric system kept coming up in Congress in the early 1900s, and being shot down. Mihm writes:

In 1916, these efforts culminated in the creation of a new anti-metric organization known as the American Institute of Weights and Measures. … Much of its success can be attributed to a sophisticated public relations campaign. It placed advertisements and editorials in industry journals; successfully lobbied hundreds of trade associations, chambers of commerce, and technical societies to go on the record condemning mandatory use of the metric system; and obsessively monitored legislation on the local, state, and national levels. When the group identified a bill that endorsed mandatory metric conversion—or merely contained clauses that opened the door to greater reliance on the metric system—it mobilized hundreds of industrialists, engineers, and managers to defeat the legislation with letters, testimony, and editorials. By the 1920s, its membership rolls included many of the most important firms in the nation as well as presidents of the National Association of Manufacturers, the Association of American Steel Manufacturers, the American Railroad Association, and other national organizations. These organizations had a stake in standardization, actively joining government-sponsored efforts to bring further uniformity to the nation’s economy over the course of the 1920s. As inch-based standards governing everything from automobile tires to pads of paper became the norm, the prospects for going metric became ever more remote. Only in scattered pockets of the business community—the electrical field, for example, and pharmaceuticals—did the metric system become dominant.

We have now reached an odd point in the US experience where two measurement systems co-exist: the inch-based traditional system, along with pint and gallons, ounces and pounds, is how most Americana talk, most of the time, in ordinary life, but the metric system is how all science and most business operates (with the exception of the building trades). Many Americans step back and forth between the two systems of measurement every day in their personal and work lives, barely noticing.

Some readers will be interested to know that this issue of Business History Review has othre paper about standardization. Here’s the list of papers. The introductory essay by Yates and Murphy is open access:

  • “Introduction: Standards and the Global Economy,” by JoAnne Yates and Craig N. Murphy (pp. 3-15)
  • “Men of Science and Standards: Introducing the Metric System in Nineteenth-Century Brazil,” by Anne G. Hanley (pp. 17-45)
  • “Inching toward Modernity: Industrial Standards and the Fate of the Metric System in the United States,” by Stephen Mihm (pp. 47-76)
  • “CE Marking, Business, and European Market Integration,” by Grace Ballor (pp. 77-108)
  • “The Business of Internetworking: Standards, Start-Ups, and Network Effects,” by Andrew L. Russell, James L. Pelkey, Loring Robbins (pp. 109-144)
  • “Making Food Standard: The U.S. Food and Drug Administration’s Food Standards of Identity, 1930s–1960s,” by Xaq Frohlich (pp. 145-176)