When did the USA introduce metric system as preferred for weights and measures?

never
205
1805
15
1866
52
1975
58
President Gerald Ford signed the Metric Conversion Act in1975. It declared the metric system "the preferred system of weights and measures for United States trade and commerce", but permitted the use of United States customary units in all activities. The metrification board was abolished in 1982 by President Ronald Reagan.
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