The expansions of the US both geographically or environmentally have been contributed by several factors. Amongst the factors that led to the expansion of the US are the 1849 California gold rush and the bowl dust in 1930s.
One of the most significant expansions of the US borders westward was the California gold rush. Before the discovery of the gold, the United States was beginning to take shape. With the purchase of Louisiana, the country was stretched all the way to the pacific and the conclusion of the Mexican American war in which California was ceded to the United States. After the discovery of gold, the word spread that California was a place where gold could be found, people from all over the country migrated to California in search of the metal. With many people believing that moving to California would guarantee them a fortune, they moved from all over the country to the area. This led to the ballooning of the population in the area from around 1000 inhabitants to around 300000 thousand prospectors in a span of seven years.
With the migration of the people looking for wealth, another group of people such as doctors, lawyers and businessmen also moved with the people because they knew the population would require their services.
The bowl dust of 1930s was an environmental catastrophe that eroded sections of the plains. It immediately and substantially reduced the agricultural land values. It was brought about by the intensive land use and the prolonged severe droughts. Although the farmers could have prevented the dust bowls by fallowing land and converting it into pastures, much of the benefits would have been captured by the neighboring farms. Due to the periodic dust blowing of soil, plains residents were afflicted by dust pneumonia and severe crop yield shocks. This led to high levels of migration in areas that were affected by the dust bowls. Immediately after the dust bowl, population substantially declined in high erosion and medium erosion counties relative to low erosion counties. This migration from these areas led to the rise of populations in other areas.
Without the occurrence of these events, it could not have been possible for mass movement of people from one region of the country to the other. Hence, these two factors led to significant expansion of the US.
Reference
Hornbeck, R. (2012). The Enduring Impact of the American Dust Bowl:Short- and Long-Run Adjustments to Environmental Catastrophe. American Economic Review , 1477-1507.
