Rain follows the plow

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Monsoon rains upon the high plains of the American West.

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 Wilber:

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.[1]

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 Plains, 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 Australia during the same period.[2]

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 that happened to coincide with settlement, an example of the logical fallacy that correlation means causation. The theory was later refuted by climatologists and is now definitively regarded as pure superstition.

North America[edit]


Out of this evidence, some scientists of the day concluded that the apparent increase in rain was due to the settlement and the effects of cultivation. One of the most prominent exponents of the theory in the United States was Cyrus Thomas, a noted climatologist. After studying the recent history of Colorado, he concluded that the increase in moisture was permanent, and that it coincided exactly with the first settlers' cultivating of the land. 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 Wilber, an amateur scientist and author.




William Gilpin, the first territorial governor of Colorado and an aide to President Lincoln, was a proponent of this theory. Gilpin was a strong believer in the idea of Manifest Destiny. One of his books was called The Mission of the North American People. He strongly promoted western settlement and invoked this theory as one of his reasons for people to migrate west.[5]


In 2007, Richard Raddatz, a climatologist at the University of Winnipeg, 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.[6]

Observed trends of Midwest summertime cooling and increased rainfall over the last third of the 20th century have been linked to agricultural practices in the arid Great Plains, in an inversion of the Dust Bowl scenario. Increased precipitation and humidity may cause the downward trend in Midwestern average daytime highs, since humid air takes more energy to heat to a given temperature than dry air. In turn, the increase in Midwestern rainfall may be driven by the large increase in land under irrigation in the Plains over the 20th century. Irrigation water enters the atmosphere through evaporation and plant transpiration, and then falls as rain over the downwind Midwest.[7]


The Kanyaka sheep farm (Flinders Ranges, South Australia) was built at a high cost in the 1850s and abandoned after the drought of 1869.[2]

At the same time that the theory existed in North America, it also existed on the farming frontier in South Australia. There was a spread of farming from the area near Adelaide northwards to areas of much lower rainfall. 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.[2]

Despite this, until further droughts in the 1880s, farmers talked of cultivating cereal crops up to the Northern Territory border. Today, however, grain crops still do not grow further north than Quorn, as advised by Goyder's original report.[2]

See also[edit]


  1. ^ "Rain Follows the Plow", Episode Seven, The West, PBS
  2. ^ a b c d Jared Diamond, Collapse, page 398, Penguin Books, 2005, ISBN 978-0-14-027951-1.
  3. ^ Marc Reisner (1986). Cadillac Desert. Penguin Books. ISBN 0-14-017824-4. 
  4. ^ cited in Which Old West and Whose?, Stanley K. Schultz and William P. Tishler
  5. ^ Wallace, Stegner (1954). Beyond the Hundredth Meridian. New York, NY: Penguin Group. pp. 1–7. ISBN 014015994 0. 
  6. ^ McAuliffe, Bill (2007-07-23). "Hot enough for ya? It could be sweaty corn". StarTribune. Archived from the original on 2007-10-23. Retrieved 2007-07-27. 
  7. ^ Crop irrigation could be cooling Midwest, Sid Perkins, ScienceNews Jan 22, 2010