The English system of measurement is older than the metric system and quite outdated, internationally. In fact, the United States is the only country where the English system of measurement is still widely in use. While the modern standard metric system (SI) has been adopted worldwide, the U.S. has not taken steps to eliminate the traditional system, as most other countries have done.
The English system was composed of a mix of local standards from Roman, Norse, Celtic and Saxon cultures. The metric system was invented in France in 1799.
The English system was originally based on non-universal things such as human body parts. An inch was the width of the thumb, an acre the amount of land that could be plowed in a day.
The purpose of the metric system was to create a universal system of measurement. It was therefore originally based on universal standards such as the properties of water and the size of the Earth.
English as Metric
According to mathematics professor Russ Rowlett, “the legal definitions of the English customary units are actually based on metric units … a yard equals exactly 0.9144 meters … a pound equals exactly 0.45359237 kilograms.”
In the U.S., metric and English systems of measurement are intermingled, often used to describe similar things. “We measure the length of a race in meters, but the length of the long jump event in feet and inches. We speak of an engine's power in horsepower and its displacement in liters,” according to Rowlett.