Square Mile (mi²)
The square mile is the area of a square with sides of one mile, equal to 640 acres or approximately 2.59 square kilometers. It is the large-area unit of the American and British measurement systems, used for cities, states, countries, and geographical features in English-speaking contexts. When Americans hear that Texas is 268,596 square miles or that Manhattan is 22.8 square miles, they instantly grasp the scale in a way that square kilometers cannot replicate for them. The square mile also has a special cultural status in London, where the City of London financial district is known simply as the Square Mile, covering roughly 1.12 square miles within the ancient Roman walls.
Definition
One square mile is the area of a square with sides of exactly one mile, where one mile is exactly 1609.344 meters. This makes one square mile exactly 640 acres, 3,097,600 square yards, 27,878,400 square feet, or approximately 2.58999 square kilometers. One square mile equals exactly 2,589,988.110336 square meters.
History
The square mile derives from the statute mile, which was defined by an English act of Parliament in 1593 as 5280 feet or 1760 yards. Squaring this gives the square mile its 640-acre equivalent. The mile itself traces back to the Roman mille passus, meaning one thousand paces, with each pace being two steps. The US Public Land Survey System, established in 1785 to systematically divide western territories, used the square mile as its fundamental unit. Each township was divided into 36 sections of one square mile each, and this grid still defines property boundaries across much of the United States. The international yard and pound agreement of 1959 fixed the mile at exactly 1609.344 meters, making the square mile exactly 2,589,988.110336 square meters.
Common Uses
American geography and demographics dominate the unit's use. State areas, county boundaries, city limits, and national park sizes are reported in square miles in US media and government publications. Population density in the United States is expressed as people per square mile. The US Census Bureau reports all area statistics in square miles. British media uses square miles for the UK and for reporting on international events to British audiences. Real estate development at the city-planning scale sometimes uses square miles to describe large projects or district areas.
Did You Know? Facts About Square Mile
- Manhattan is about 22.8 square miles, roughly the same area as San Marino, one of the smallest countries in the world.
- Alaska is the largest US state at 665,384 square miles, about 425 times larger than Rhode Island at 1,545 square miles.
- The City of London financial district, known as the Square Mile, actually covers about 1.12 square miles. The nickname predates precise measurement.
- One square mile contains exactly 640 acres. This neat number comes from the land survey system, where a section of 640 acres was designed to be subdivided into halves, quarters, and so on.
- The entire surface area of the Earth is about 197 million square miles, of which about 57 million is land and 140 million is water.