How was it determined that the length...

The statute mile of 5,280 feet originated in the Roman mille passus, or “thousand paces,” which measured 5,000 Roman feet. A Roman pace equaled 5 Roman feet, measured from the point at which the heel of one foot was raised to the point at which it was set down again after an intervening step by the other foot. Around the year 1500, the mile was divided into 8 furlongs, with each furlong measuring 625 feet. Later, under Queen Elizabeth I, the Statute of 1593 confirmed the use of a shorter foot, which made the length of a furlong 660 feet, adding another 280 feet to the mile.