What were the which encouraged the farmers for a dramatic expansion of wheat production in the late nineteenth century in USA? What were its effects?

(a) The factors for expansion of wheat production were as follows:
(i) Growth in urban population.
(ii) Bigger export market.
(iii) Rising prices of wheat encouraged farmers to produce wheat.
(iv) Spread of railways made it easy to transport grain to the eastern coast for export.
(v) World War I and higher demand with boom in the market.
(vi) Russian supplies of wheat were cut off and USA had to feed Europe. US President Wilson called upon farmers to respond to the need of the time. “Plant more wheat, wheat will win the War”, he said.
(b) Effects : The area under wheat cultivation increased from 45 million acres of land in 1910 to 74 million acres nine years later. The increase was particularly in the Great Plains where some big farmers or wheat barons controlled as much as 2,000 to 3,000 acres of land individually.