Final answer:
Between 1870 and 1890, wheat prices experienced a significant drop from two dollars to forty cents per bushel caused by overproduction and an oversupply in the market which resulted in commodity prices falling.
Step-by-step explanation:
The period between 1870 and 1890 was characterized by fluctuations in the price of wheat. After the prosperity for farmers during and after World War I due to high commodity prices, the situation began to change. The prosperity led to a land rush and expansion of farming operations to maximize profits. However, with the end of World War I, the price of wheat started to drop significantly, as the previous high demands decreased. By the end of 1929, the price of wheat plummeted from two dollars to forty cents per bushel, mostly due to the overproduction and subsequent oversupply that resulted in lower prices.
Similarly, during the 1920s, as commodity prices fell and farms faced foreclosures due to the inability to repay loans, there was a significant decline in wheat prices. This impact was part of a larger economic strain on the agricultural sector that eventually led to the Great Depression.