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Rain follows the plow is the conventional name for a now-discredited theory of climatology that was popular throughout the American West and Australia during the late 19th century. The phrase was employed as a summation of the theory by Charles Dana Wilbur:God speed the plow.... By this wonderful provision, which is only man's mastery over nature, the clouds are dispensing copious rains ... [the plow] is the instrument which separates civilization from savagery; and converts a desert into a farm or garden.... To be more concise, Rain follows the plow.

The basic premise of the theory was that human habitation and agriculture through homesteading, effected a permanent change in the climate of arid and semi-arid regions, making these regions more humid. The theory was widely promoted in the 1870s as a justification for the settlement of the Great Plainsmarker, a region previously known as the "Great American Desert". It was also used to justify the expansion of wheat growing on marginal land in South Australiamarker during the same period.

According to the theory, increased human settlement in the region and cultivation of soil would result in an increased rainfall over time, rendering the land more fertile and lush as the population increased. As later historical records of rainfall indicated, the theory was based on faulty evidence arising from brief climatological fluctuations. The theory was later refuted by climatologists and is regarded as a serious error. In South Australia, George Goyder warned as early as 1865, in his famous report on farming in the state, that rain would not follow the plow. Despite this, there was talk of cereal crops spreading to the Northern Territory border up until further droughts in the 1880s. Today, however, grain crops do not grow further north than Quornmarker.


The theory arose in the late 1860s and 1870s during the westward expansion of white settlement west of the Missouri Rivermarker and across the 100th meridian west. This was the traditional boundary line between the humid and semi-arid portions of central North America. Specifically, in the early part of the decade, white settlement had spread into central and western Nebraskamarker along the Platte River. Emigrants on the Oregon Trail began reporting that the land in western Nebraska, previously known for its yellowed dry vegetation during the summer, had seemingly become green. At the same time in Australia, there was a spread of farming from the area near Adelaidemarker northwards to areas of much lower rainfall.

Out of this evidence, some scientists of the day concluded that change was due to the settlement and the effects of cultivation. One of the most prominent exponents of the theory was Cyrus Thomas, a noted climatologist who studied the recent history of Colorado, concluding the increase in moisture was permanent, and that it coincided exactly with the first homesteaders. Other prominent advocates of the theory were Ferdinand Vandeveer Hayden, the noted geographer who had explored and surveyed parts of the Rocky Mountains of Colorado; Samuel Aughey, a professor at the University of Nebraska; and Charles Dana Wilbur, an amateur scientist and author.

Thomas and other climatologists offered a variety of explanations for the theory. A common idea was that the plowing of the soil for cultivation exposed the soil's moisture to the sky. In addition, newly planted trees and shrubs increased rainfall as well, as did smoke from trains. Another hypothesis stated that the increased vibration in the atmosphere due to human activity created additional clouds, from which rain fell. This idea led to the widespread dynamiting of the air across the Great Plainsmarker in the 1870s.

The theory was widely embraced in its day, not only by scientists, but land speculators and emigrants. Some historians have argued that the theory was embraced readily as an outgrowth of Manifest Destiny, the idea that the United States had a mission to expand, spreading its form of democracy and freedom. The theory is regarded as partially responsible for the rapid settlement of the Great Plains in the later 19th century. In 'The Great Valleys and Prairies of Nebraska and the Northwest', published in 1881, Charles Wilber wrote:In this miracle of progress, the plow was the unerring prophet, the procuring cause, not by any magic or enchantment, not by incantations or offerings, but instead by the sweat of his face toiling with his hands, man can persuade the heavens to yield their treasures of dew and rain upon the land he has chosen for his dwelling... ...The raindrop never fails to fall and answer to the imploring power or prayer of labor.

Climatologists now understand that increased vegetation and urbanization can result in increased precipitation. The effect, however, is local in scope, with increased rainfall typically coming at the expense of rainfall in nearby areas. It cannot result in a climatological change for an entire region. They also understand that the Great Plains had had a wetter than usual few seasons as this theory and settlement were both taking place. When normal arid conditions returned, homesteaders were damaged.

In 2007, Richard Raddatz, a climatologist at the University of Winnipegmarker, published results of his studies on the conversion of Canadian grasslands to cropland. His theory is that, because corn crops transpire moisture into the atmosphere at a faster rate than the grass they have replaced, crops can generate storms and intensify the season during which water can cycle through the atmosphere.

See also



  1. Rain Follows the Plow, Episode Seven of The West, PBS
  2. Jared Diamond, Collapse, page 398, Penguin Books, 2005, ISBN 978-0-140-27951-1.
  3. cited in Which Old West and Whose?,Stanley K. Schultz and William P. Tishler

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