The United States still, for most purposes, uses the traditional, non-metric units which swere mainly inherited from England. Over the course of time, changes have been made on both sides of the Atlantic so that the British Imperial units came to differ, in some cases, from similarly-named United States customary units. However, in the 1950s, agreements were made between the U. S. and Commonwealth of Nations countries that in many cases brought about identity between BI units and similarly-named United States customary units. Some differences remain, particularly in units of capacity and weight or mass.

Bushel Table of States

A table of weights from the secretaries of the different states, showing the number of pounds which their laws recognize as a bushel of different commodities. c. 1854

As the Commonwealth countries have decided separately to move toward the use of metric (mainly SI) units, the U. S. more and more becomes the last refuge of its customary unit system. But in this regard, it is not likely to change. Attempts have been made to change the U. S. to metric usage, and in some things (for example, alcoholic beverage containers), metric sizes have become required by law. However, the public in the U. S. appears to prefer staying with the customary units.

Platinum-Iridium meter bar

The U.S. Standard Meter, in use until 1960: many U.S. customary units are defined in terms of the SI meter.

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