On the US adopted the International Nautical Mile in lieu of the US Nautical Mile.
Miles derived from the length of a degree of an Earth meridian — called nautical miles, meridian miles, geographical miles, or sea miles — go back thousands of years. They have had many values, typically based on 10, 12, 15, or 60 miles to a degree of a great circle. The British and US nautical miles were each derived by taking 60 nautical miles per degree, but their values were nevertheless not the same.
In 1929 the International Hydrographic Bureau obtained an agreement from a large number of countries to adopt a value of 1852 metres for the nautical mile, the unit thus defined to be called the International Nautical Mile. However, a few countries, including the US, chose not to accept the new value.
In 1953 the Department of Defense and Department of Commerce considered and adopted a proposal to switch to the new value for the nautical mile. Officially, as of , the nautical mile in the US was defined to be 1852 metres, replacing the previous value of 1853.248 metres. (The “old” US nautical mile had also been defined in terms of metres ever since the Mendenhall Order of 1893, although that order rounded the value to 1853.25 m.)
For more details, read the 1954 NBS announcement of the adoption of the International Nautical Mile.
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