When was the international standard of the "mile" adopted?

It is well known that one mile is equal to 5,280 feet or 1,760 yards. It may be less well known that the actual value of this unit of length was standardised only comparatively recently. In October 1958, the International Committee on Weights and Measures recommended that the metre be defined in atomic terms. On 1 July 1959, the United States, United Kingdom, Canada, Australia, New Zealand and the Union of South Africa then agreed to the definition of the mile in terms of this standard: one mile equals 1,609.344 metres.

The word "mile" is also used to describe a wide range of units derived from the Roman mile, such as the nautical mile (now exactly 1.852 kilometres), the Italian mile (roughly 1.852 kilometres), and the Chinese mile (now 500 metres exactly). The Romans divided their mile into 5,000 Roman feet but the greater importance of furlongs in pre-modern England meant that the statute mile was made equivalent to 8 furlongs or 5,280 feet in 1593. This form of the mile then spread to the British-colonised nations some of which continue to employ the mile. The US Geological Survey now employs the metre for official purposes, but legacy data from its 1927 geodetic datum has meant that a separate "US survey mile" continues to be used.

While most countries replaced the mile with the kilometre when switching to the International System of Units, the international mile continues to be used in some countries, such as Liberia, the United Kingdom and the United States.