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.
In The 1800s, Governments Of New Nations Were Eager To Adopt Standards That Aligned Them With Western Europe
While the United States struggled to find uniformity, several countries around the world enthusiastically accepted the metric system. Metrication, as it's known, accompanied decolonization as it took place around the world.
Eleven of the first 20 countries to adopt the metric system after France were located in Latin America. Chile made the metric system optional in 1848, fully adopting the standards in 1865. Additional countries like Mexico, Colombia, and Venezuela similarly adopted the metric system during the 1850s.
Countries throughout Western Europe began to follow the metric system, with Portugal, Belgium, and the Netherlands serving as the earliest adopters. Further east, Romania, Austria, Serbia, and Hungary all began to use metric standards by 1874.
By switching to the metric system, individual nations found themselves on common ground with political counterparts and potential economic partners. As a means of opening up financial opportunities, the adoption of metric standards was often done at the expense of popular opinion.
In 1875, The US Signed The Treaty Of The Metre, Which Established The Metric System For International Trade
What the US fostered during the 19th century became a blended system of weights and measures. While resistance to the metric system remained strong in some contexts, the government made it legal for manufacturers and the like to use customary units or metric standards for measurement. In conjunction with the passage of the Metric Act of 1866, the federal government issued each state a set of metric standards for length, mass, and capacity.
Nine years later, the US was one of 17 countries to sign the Treaty of the Metre, an agreement that set up the permanent body called the International Bureau of Weights and Measures. Based in France, the Bureau International des Poids et Mesures, or BIPM, was tasked with assessing metric standards, prototypes, and instruments around the world.
The agreement was ratified by the US Senate and went into effect in the US in 1878. The document was amended in 1921, at which time 44 countries agreed to participate.
In The Early 1900s, US Scientists Pushed For Metric Conversion, But The Public Wanted The US To Lead, Not Follow
Scientists and medical professionals have been especially vocal in calls for change. Congressional testimonies in favor of metrication by the likes of Alexander Graham Bell, Melvil Dewey, and Thomas Edison attest to the importance of the issue. In 1906, Bell identified a series of issues presented by not adopting the metric system and presented Congress with arguments as to why it was beneficial for the workforce, scientific investigation, trade, and commerce.
The head of the newly established National Bureau of Standards (set up in 1901), Samuel W. Stratton, supported use of the metric system, especially in scientific settings, while representatives from engineering firms, wholesale grocers, and academic and professional associations came together before Congress to push for standardization in 1921.
Despite multiple avenues for support of uniformity, politicians could not deny the public sentiment that the United States should remain at the forefront of change, not adopt an expensive, elitist system from abroad.
Congress Waited Until 1975 To Pass The Metric Conversion Act, Which Called For (But Didn’t Mandate) The Metric System In The US
The Metric Conversion Act of 1975, signed by President Gerald Ford, "designated the metric system of measurement as the preferred system of weights and measures for United States trade and commerce." While the act specified 1992 as the date by which federal agencies "use the metric system of measurement in its procurements, grants, and other business-related activities," it also allowed for "the continued use of traditional systems of weights and measures in non-business activities."
Going into effect more than 100 years after use of the metric system had become legal in the United States, the act also established the United States Metric Board. The board was tasked with publicizing, encouraging, and facilitating understanding and use of the metric system, but had no compulsory powers.
Many businesses did convert, educational programs were introduced, and public television even featured programs to teach Americans about the metric system. However, using the metric system remained completely voluntary.