how much corn is in everything, Michael Pollan visited a corn farm in Iowa. He described how once upon a time farms grew a variety of crops, including oats and hay for their farm animals. Now most farms in the Midwest grow only corn and soybeans, and each feed an average of 129 people. Even though farmers like George Naylor, who Michael Pollan shadows, are statistically some of the most productive humans ever (in regards to terms of output per worker), they can hardly afford to support their family living on the farm.
In George Naylor's case, they are only able to survive because of his wife's job and an annual government subsidy. They cannot live on their crops; even though Iowa is predominantly farmland, 80% of their food is imported. Before any of the crops reach other people, it must be processed or fed to livestock. Yes, even the soybeans are now in 2/3 of all processed foods.
So how did corn (and soybeans) become such a large part of Iowa? After the invention of the tractor, horses were no longer needed (nor were the crops that fed them). Because corn prices soared and brought in the most money, farmers devoted more and more space to that particular crop (with soybeans being in rotation).
Of course, with all of the farmers doing this, the price of corn declined. Instead of planting something different, farmers just planted more corn.
In the 1950s and 1960s, there was so much cheap corn, that industrial farmers began feeding cows and chickens on feedlots and factories with corn. The farmers in Iowa couldn't compete, so they got rid of their cows and chickens and planted even more corn. By the 1980s, corn was the dominant crop in Iowa.
It even pushed the people out. Corn and soybeans are simple crops and don't require as much human labor as the old farms did. "Growing corn is just riding tractors and spraying [pesticides]," according to farmer George Naylor. Riding and spraying crops for 500 acres can be counted in weeks, so the people go elsewhere for work.
Of course this is a simplified tale. Of course the government had a role in helping corn become the monster crop it is today.