The Metric System: Us Legalization Timeline

The metric system was legalised in the US in 1866, when the Metric Act was passed by Congress and signed into law by President Andrew Johnson. However, the US has never fully adopted the metric system, and US customary units remain in common use.

The Metric Act of 1866

The Act was codified as 15 USC 204 et seq. It stated that it was:

> "lawful throughout the United States of America to employ the weights and measures of the metric system; and no contract or dealing, or pleading in any court, shall be deemed invalid or liable to objection because the weights or measures expressed or referred to therein are weights or measures of the metric system."

The Act also included a now-obsolete definition of the metric system and tables of units.

The metric system was already in use in some industries in the US, and Kasson's report to Congress stated that it was "especially adapted to the wants of others". He also noted that the metric system was already being used in the US Coast Survey.

In 1875, the US became one of the original 17 signatory nations of the Metre Convention, also known as the Treaty of the Metre. This treaty established the International Bureau of Weights and Measures (BIPM) in Sèvres, France, to provide standards of measurement for worldwide use.

The US Congress has established a national policy of increasing the voluntary use of the metric system as the preferred system of measurement for trade and commerce. All US agencies are required to adopt the metric system, and the US law permits the use of either the SI (International System of Units) or the US customary measurement system.

The Metric Conversion Act of 1975 declared the metric system "the preferred system of weights and measures for United States trade and commerce", but permitted the use of US customary units in all activities. This act also established the United States Metric Board to plan, coordinate, and educate the US people for the Metrication of the United States. The Metric Board was abolished in 1982.

The Omnibus Trade and Competitiveness Act of 1988

The US legally recognised the metric system of measurement in 1866, with the passing of the Metric Act. This Act, also known as the Kasson Act, included a now-obsolete definition of the metric system and tables of units. In 1975, the US further solidified its commitment to the metric system with the Metric Conversion Act, declaring it as "the preferred system of weights and measures for United States trade and commerce".

Now, onto the Omnibus Trade and Competitiveness Act of 1988:

The Act, also known as H.R. 4848, included modifications to the Harmonized Tariff Schedule, which the President was to implement at the earliest practicable date. These modifications aimed to bring trade agreements in line with the standards set by the Convention and to reflect tariff reductions resulting from various trade negotiations and agreements.

The Act also outlined the role of the United States Trade Representative, who would advise the President and Congress on matters related to international trade, coordinate interagency resources for specific unfair trade practice cases, and make reports to Congress on relevant matters.

Additionally, the Act addressed the process for initiating investigations into unfair trade practices, with the Trade Representative determining whether an investigation would be detrimental to US economic interests. The Act further detailed how the President could develop trade policy and priorities, with the Commission providing investigations and reports as requested by the President or the Trade Representative.

Overall, the Omnibus Trade and Competitiveness Act of 1988 sought to enhance the competitiveness of American industry and address trade-related issues, including tariffs and unfair trade practices.

The Metric Conversion Act of 1975

The Act also established the United States Metric Board, which included representatives from scientific, technical, and educational institutions, as well as state and local governments. The Board's purpose was to plan, coordinate, and educate the U.S. people for the Metrication of the United States.

The Metric Board was abolished in 1982 by President Ronald Reagan, largely on the suggestion of Frank Mankiewicz and Lyn Nofziger. Despite this, the U.S. still has a national policy to adopt the metric system, and all U.S. agencies are required to adopt it.

Executive Order 12770

The order directed all executive branch departments and agencies to take all appropriate measures within their authority to carry out the provisions of the order. This included using the metric system in federal government procurements, grants, and other business-related activities, to the extent economically feasible by September 30, 1992, or by a later date established in consultation with the Secretary of Commerce. It was recognised that metric usage would not be required if it was impractical or likely to cause significant inefficiencies or loss of markets for US firms.

The order also emphasised the importance of education and guidance in increasing understanding of the metric system. Departments and agencies were instructed to seek out ways to enhance cooperation with industry, especially small businesses, as they voluntarily converted to the metric system. Additionally, they were to designate a senior-level official as the Metric Executive to assist in implementing the order and act as a liaison with other government agencies and private sector groups.

Overall, Executive Order 12770 played a key role in advancing the use of the metric system in the United States by directing federal agencies to take concrete steps towards its implementation and ensuring coordination among the various departments and agencies involved.

The Mendenhall Order of 1893

The Mendenhall Order marked a decision to change the fundamental standards of length and mass in the United States from the customary standards based on those of England to metric standards. The metric standards were developed through international cooperation under the auspices of the International Bureau of Weights and Measures (BIPM). The BIPM was established in Sèvres, France, in 1875, when the United States was one of the original seventeen signatory nations to the Metre Convention, also known as the Treaty of the Metre.

The Mendenhall Order stated that the international metre and kilogram would be regarded as the fundamental standards of length and mass in the United States, for both metric and customary weights and measures. This decision was a departure from the previous policy of attempting to maintain standards identical to those of Great Britain. The order also included tables for converting customary and metric weights and measures.

The definitions of United States customary units, such as the foot and pound, have been based on metric units since the Mendenhall Order. However, the Mendenhall Order did not require anyone outside of the Office of Weights and Measures to switch from customary units to the metric system.

The Metric Conversion Act of 1975, signed into law by U.S. President Gerald Ford, later declared the metric system "the preferred system of weights and measures for United States trade and commerce". However, the use of customary units was permitted, and conversion was to be "completely voluntary".

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