Short answers, pulled from the story.
The Roman mile was established by Agrippa in 29 BC. This unit relied on the Roman foot to measure a distance of 5,000 feet and created a standard that would echo through two millennia of history. Surveyors equipped with specialized tools like the decempeda and dioptra spread this measurement across the vast network of 50,000 Roman miles of stone-paved roads that radiated from the Forum.
Parliament passed the Act on the Composition of Yards and Perches in 1593 during the reign of Queen Elizabeth I. This legislation increased the number of feet within the mile to 5,280 to avoid a significant tax increase for landowners and surveyors. The decision maintained the mile at 8 furlongs where each furlong contained 40 poles and each pole held 16 and a half feet.
The international mile was born from a diplomatic agreement on the 1st of July 1959. The United States, the United Kingdom, Canada, Australia, New Zealand, and the Union of South Africa resolved to standardize the yard as exactly 0.9144 meters. This agreement established the mile as exactly 1,609.344 meters and eliminated small but measurable differences that had arisen from separate physical standards.
The US National Geodetic Survey and the National Institute of Standards and Technology announced their joint intent to retire the US survey foot and US survey mile in October 2019. The change takes effect on the 1st of January 2023 to finally phase out the legacy data from the 1927 geodetic datum. This decision ends the use of the US survey mile which is defined as 5,280 US survey feet or 1,609.347 meters.
Since 1929, the international nautical mile has been defined by the First International Extraordinary Hydrographic Conference in Monaco as exactly 1,852 meters. This standard approximates one minute of latitude and serves as the basis for aeronautical and maritime navigation. The United States previously defined the nautical mile in the 19th century as 6,080.2 feet while the United Kingdom defined the Admiralty nautical mile as 6,080 feet.
The international mile continues to be used in the United Kingdom, the United States, and a number of countries with fewer than one million inhabitants. These include territories such as American Samoa, the Bahamas, Belize, and the Falkland Islands which are UK or US territories. In Canada, the mile is encountered predominantly in rail transport and horse racing even though roadways have been metricated since 1977.