Acre

• 1. Introduction

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  The acre is a unit of land area, and its origin is a man with a team of eight oxen and a single day of light. In the Middle Ages, an acre was imagined as the amount of ground that one ploughman and his eight oxen could turn over before nightfall. There is no fixed shape to it. Any patch of 43,560 square feet qualifies, whether it is a long thin ribbon or a near-perfect square. That square would run about 208 feet 9 inches on each side. Behind that flat figure sits a tangle of competing definitions, vanished European cousins, and a quiet legal argument that took until 2010 to settle in one country. How did a measure built around oxen survive into the age of the metre? Why do the United States keep two different acres that disagree by a hair? And why would a landowner say he held 32,000 acres rather than 50 square miles?

• 2. Anatomy Of A Furrow

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  Forty perches long and four perches wide. That was the original shape of an acre, a strip stretching 660 feet by 66 feet. The length, one furlong, takes its name from the phrase a furrow long, the distance an ox team could pull a plough before turning. The width, four perches or 66 feet, completes the parcel. Ten square chains make up the same area, where a chain measures 66 feet, or 22 yards, or 4 rods, or 100 links. Pour those units together and the totals all agree. One acre equals 4,840 square yards, or 43,560 square feet, or 160 perches, or 4 roods. A perch is a square rod, and a single square rod works out to 0.00625 of an acre. Slot the acre into the larger grid and the relationships keep clicking. It takes 640 acres to fill one square mile, and a mile itself runs 5,280 feet, or 1,760 yards. The shape stays free even as the size stays fixed, which is why surveyors could lay an acre across any terrain that suited them.

• 3. Two American Acres

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  In 1959, the United States and five Commonwealth nations signed the international yard and pound agreement, fixing the international yard at exactly 0.9144 metre. The United States kept a loophole. American authorities ruled that the US survey foot, and the survey acre built on it, would continue until it became desirable and expedient to readjust it. So the country carried two acres at once. The international acre measures about 4,046.856 square metres. The US survey acre measures about 4,046.872 square metres, its value tied to an inch set by the Mendenhall Order of 1893, which declared one metre equal to 39.37 inches exactly. The gap between them is about four parts per million. In real terms the difference comes to 0.016 square metres, around 24.8 square inches, roughly a quarter of an A4 or US letter sheet. Land is rarely measured precisely enough for anyone to notice. The arrangement was always called temporary, and in October 2019 the National Geodetic Survey and the National Institute of Standards and Technology announced they would retire the US survey foot, mile, and acre at the end of 2022.

• 4. The Word And Its Cousins

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  The word acre first appears in 1006, in a text from Fécamp in Normandy, where it carried the meaning of an agrarian measure. It descends from the old Scandinavian akr, meaning cultivated field or ploughed land. The same root lives on in the Icelandic and Faroese akur, the Norwegian and Swedish åker, the Danish ager, and the German Acker. It reaches further still, to the Latin ager, the Sanskrit ajr, and the Greek agros. The English language once spelled it aker before that form fell out of use. Across Europe, other countries measured their fields by their own acres under other names. In Germany, the Netherlands, and Eastern Europe, the equivalent was the Morgen, a strip of ploughland a man and an ox or horse could turn in a morning. The Morgen too splintered into many regional values, and travelled as far as Old Prussia, the Balkans, Norway, and Denmark. The shared idea behind every version was the same: a day or a morning of one man's labour, frozen into a number.

• 5. The Normandy Acre

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  Before the metric system, France measured ground mainly in the arpent carré, a unit rooted in the Roman system. The acre proper survived only in Normandy and a few neighbouring areas, and even there it refused to settle. Its value swung from 3,632 to 9,725 square metres, with 8,172 square metres turning up most often. Within a single Norman district it could still split in two. In the pays de Caux, farmers were still distinguishing the grande acre of 68 ares and 66 centiares from the petite acre of 56 to 65 centiares well into the 20th century. The Normandy acre divided into 4 vergées, the local roods, and 160 square perches, mirroring the English layout. It equalled 1.6 arpents, the unit favoured across northern France beyond Normandy. That distinction crossed the Atlantic and caused confusion. In Quebec, the Paris arpent used before the metric era is sometimes called the French acre in English, yet the Paris arpent and the Normandy acre were entirely different units, and the Normandy acre never reached French Canada at all.

• 6. Statutes And Estates

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  The Act on the Composition of Yards and Perches, dating from around 1300, fixed the acre at 40 perches in length and four in breadth, which is 220 yards by 22 yards. English and later British monarchs kept legislating it. Statutory values were enacted under Edward I, Edward III, Henry VIII, George IV, and Queen Victoria, whose British Weights and Measures Act 1878 defined the acre as 4,840 square yards. The acre also shaped how people spoke about owning land. In the United Kingdom, the size of farms and estates was usually given in acres, or in acres, roods, and perches, even when the figure grew enormous. A landowner with 50 square miles would be described as holding 32,000 acres instead. The same logic gridded the New World. Across the western United States, western Canada, the Canadian Prairie Provinces, and the US Midwest, land was surveyed on square-mile blocks. Quarter a square mile and each piece holds 160 acres; quarter that again and each piece holds 40 acres. That last unit gave American farms the phrase the back 40, the 40-acre parcel at the rear of the property.

• 7. The Acre's Long Retreat

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  On the 1st of October 1995, the acre lost its standing as a primary unit for trade in the United Kingdom. A 1994 amendment to the Weights and Measures Act replaced it with the hectare. One exemption held on. Land registration, which records the sale and possession of land, kept the acre until HM Land Registry ended that exemption in 2010. Even now the acre survives as a supplementary unit, lawful indefinitely beside the hectare, and the farming and property trades still use it informally to talk to the public. The pattern repeats across the former Commonwealth. The acre persists by custom in dozens of places, from Antigua and Barbuda to Ghana to the Falkland Islands, and lingers as a statute measure in only a few. It dropped out of statute decades ago in Australia, New Zealand, and South Africa. In the Republic of Ireland, the hectare is the legal unit under European directives, yet the acre, in the standard British form rather than the larger old Irish acre, still dominates farm talk. Elsewhere the unit has fractured into local descendants worth tracking on their own.

• 8. A Field Of Variants

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  The Scottish acre ran to 1.3 imperial acres, about 5,080 square metres, before it became obsolete. The old Irish acre held 7,840 square yards, and the Cheshire acre stretched to 10,240. Outside the British world, the names multiply. The Greek stremma once meant roughly 10,000 square Greek feet but now sits at exactly 1,000 square metres, and the Turkish dunam, once about 1,600 square Turkish paces, has been fixed at the same 1,000. The Roman actus quadratus covered about 14,400 square Roman feet, or some 1,260 square metres, while the Middle Eastern feddan stands at 4,200 square metres. In Puerto Rico, the cuerda is sometimes called the Spanish acre on the US mainland. Two modern coinages show the unit still bending to convenience and to marketing. The town acre appeared in early 19th-century grid plans for places such as Adelaide, Wellington, New Plymouth, and Nelson, where land was carved into imperial-acre plots. The builder's acre is blunter: 40,000 square feet, a flat 200 by 200 feet, used in US real estate to round off the arithmetic. It runs nearly 10 percent short of a survey acre, and that shortfall has produced lawsuits alleging misrepresentation.