The causes of the Great Depression were over speculation, over plating by farmers which made crop prices go down, people were over borrowing credit and not paying it, and people were also taking out loans and not paying those back
After the war of 1812, the first expansionist goal of the republic was the acquisition of Florida, since this was the closest and most attainable area next to New England. Although they would soon seek California.
It was the internal reforms of Mikhail Gorbachev, the last Soviet leader that led to the end of the Cold War
