Square Mile
Symbol: mi²United States, United Kingdom
Was ist ein/eine Square Mile (mi²)?
The square mile (symbol: mi² or sq mi) is a unit of area in the imperial and US customary systems, defined as the area of a square with sides of one mile (5,280 feet or 1.60934 km). One square mile equals exactly 640 acres, 27,878,400 square feet, or approximately 2.58999 square kilometers.
Large-Scale Imperial Unit
The square mile is the standard large-area unit in the United States and United Kingdom, serving the same role that the square kilometer plays in metric countries. US states, counties, cities, national parks, and geographic features are all measured in square miles. Population density in the US is expressed as people per square mile.
The Section
In the US Public Land Survey System, one square mile is called a "section." The entire western United States was divided into sections during the 19th century for orderly settlement. This grid pattern is still visible today in the straight-line boundaries of farms, roads, and counties across the American Midwest and West.
Etymology
The Mile
The word "mile" comes from the Latin "mille passus" (a thousand paces), where a Roman pace was a double step of about 5 Roman feet. The Roman mile was therefore about 4,854 modern feet. The English statute mile, defined by Parliament in 1593 as 5,280 feet, is longer than the Roman original.
Square Mile
The term "square mile" simply denotes the area of a square measuring one mile on each side. The concept has been used in English land measurement since at least the medieval period, though the exact size of a mile — and therefore a square mile — varied until statutory standardization.
'The Square Mile'
In British English, "the Square Mile" (capitalized) specifically refers to the City of London — the historic core of London with an area of approximately 1.12 square miles. This usage dates to the medieval period when the City's jurisdiction was roughly one mile square.
Precise Definition
One square mile is defined as the area of a square whose sides each measure one statute mile (exactly 5,280 feet or 1,609.344 meters). This equals exactly 27,878,400 square feet, 3,097,600 square yards, 640 acres, and approximately 2.58999 square kilometers.
Key Conversions
1 mi² = 640 acres = 27,878,400 ft² = 3,097,600 yd² ≈ 2.590 km² ≈ 259.0 hectares. Inversely: 1 km² ≈ 0.3861 mi², 1 hectare ≈ 0.003861 mi².
The 640-Acre Relationship
The fact that 1 square mile = 640 acres exactly is fundamental to American land law. It follows from: 1 mile = 80 chains, 1 mi² = 6,400 square chains, and 1 acre = 10 square chains, giving 6,400/10 = 640 acres per square mile.
Geschichte
English Origins
The square mile has been used as a land area measure in England since at least the 13th century, though the mile's definition varied over time and by region. The statute mile of 5,280 feet was established by the English Parliament in 1593, standardizing the square mile at its current size.
American Land Survey
The square mile achieved its greatest importance through the US Public Land Survey System, established by the Land Ordinance of 1785 under Thomas Jefferson's influence. This system divided federal territory into a grid of 6-mile-square townships, each subdivided into 36 one-square-mile sections. Each section (640 acres) was further divided into quarter sections (160 acres), which became the standard homestead.
This grid system shaped the physical landscape of the American West: county boundaries, roads, fence lines, and property boundaries follow the section grid. Flying over the Midwest, the checkerboard pattern of one-mile squares is clearly visible from the air.
Census and Statistics
The US Census Bureau has reported state and county areas in square miles since the first census in 1790. Population density per square mile became a standard statistical measure. These conventions continue today, making the square mile essential to American geographic data.
Modern Persistence
While the square kilometer is the international standard, the square mile shows no signs of disappearing from American usage. US government agencies, media outlets, and the general public all use square miles for geographic areas.
Aktuelle Verwendung
United States
The square mile is used throughout the US for geographic areas. State areas (Texas: 268,596 mi²), city areas (Houston: 671 mi²), county areas (San Bernardino County: 20,105 mi²), and national park areas (Yellowstone: 3,471 mi²) are all reported in square miles. Population density is expressed as people per square mile — New Jersey leads US states at about 1,263/mi².
United Kingdom
The UK uses square miles in everyday geographic descriptions and media. News reports, Wikipedia articles, and general reference works give areas in square miles for British audiences, though official statistics may use square kilometers.
The City of London
"The Square Mile" refers specifically to the City of London, the historic financial district. Despite its name, the City's area is actually about 1.12 square miles (2.90 km²). This usage is universally understood in British English and has become a metonym for the UK financial industry.
Mapping and Navigation
US topographic maps, road atlases, and outdoor recreation maps use square miles (or fractions thereof) for area references. The township-range-section system used in legal land descriptions is based on the square-mile section.
Everyday Use
Geographic Literacy
Americans encounter square miles primarily in geographic context — learning state areas in school, reading news about disaster zones, or comparing city sizes. Alaska (663,300 mi²) is about 425 times larger than Rhode Island (1,545 mi²). Such comparisons are everyday cultural knowledge in the US.
Disaster and Event Areas
News coverage of hurricanes, wildfires, floods, and oil spills reports affected areas in square miles for American audiences. The 2010 Deepwater Horizon oil spill covered about 2,500 square miles of the Gulf of Mexico. The 2020 Australian bushfires burned about 72,000 square miles (186,000 km²).
Walking and Driving Scale
A square mile is roughly a 15-20 minute walk across, or about a 2-minute drive through. A city block in a typical American grid city covers about 0.01-0.02 square miles. These familiar scales help Americans gauge distances and areas intuitively.
Property and Development
Large real estate developments, master-planned communities, and ranch properties may be described in square miles. The Irvine Ranch in California spans about 93,000 acres (145 mi²). King Ranch in Texas covers about 1,289 square miles.
In Science & Industry
US Geographic Research
US-focused geographic research, urban studies, and environmental science may report areas in square miles when the primary audience is American. US Geological Survey (USGS) publications frequently use square miles for watershed areas, volcanic hazard zones, and geological formations.
Census and Demographics
US demographic research uses population per square mile as a standard density measure. The Census Bureau provides detailed square-mile data for every geographic unit in the country, from census blocks to the nation as a whole.
Ecology
US wildlife management uses square miles for home ranges and habitat areas. A grizzly bear's home range might be 100-300 mi², a wolf pack's territory 50-120 mi², and a cougar's range 50-150 mi². Wilderness area designations and conservation planning also use square miles.
Oceanography
The extent of ocean phenomena (algal blooms, oil spills, ice coverage) is sometimes reported in square miles for American audiences, though square kilometers are standard in international scientific publications.
Interesting Facts
The US township-range-section system divided 1.8 billion acres of public land into square-mile sections — the largest systematic land survey in world history, spanning from the Appalachians to the Pacific.
Manhattan has an area of about 22.8 square miles and is home to 1.6 million people, giving it a density of about 70,000 people per square mile — one of the highest in the Western Hemisphere.
The City of London (the Square Mile) has a resident population of only about 9,700 people but a daytime working population of about 513,000 — a 52-fold daily increase.
Rhode Island, the smallest US state at 1,545 square miles, could fit inside Alaska (663,300 mi²) about 425 times.
The US state of Wyoming has a lower population density (about 5.8 people/mi²) than Mongolia (about 5.2 people/mi²), making parts of the American West among the most sparsely populated places in the developed world.
A standard US survey township (36 square miles) contains 23,040 acres — enough to feed roughly 4,600 people if converted entirely to high-yield cropland.
The Pacific Ocean covers approximately 63.8 million square miles — more than all the land on Earth combined (57.5 million mi²).
Vatican City at 0.17 square miles and Monaco at 0.78 square miles are both smaller than a single section of US public survey land (1.00 square miles).
Regional Variations
United States
The square mile is the standard large-area unit in all American contexts — government, media, education, and everyday life. No serious proposal for switching to square kilometers exists.
United Kingdom
British usage of square miles persists in everyday life and media, though official statistics increasingly use square kilometers. The dual system reflects the UK's incomplete metrication.
Other English-Speaking Countries
Canada, Australia, and New Zealand have largely switched to square kilometers for official and everyday use. Square miles may still appear in historical references or when communicating with American audiences.
International Context
The square kilometer is the universal international standard. When American media report areas in square miles for domestic audiences, international editions often convert to square kilometers. The conversion factor (1 mi² ≈ 2.59 km²) is well-known to international journalists.