In the Modern Age there’s the end of the frontier (Americans were told the frontier because their land was unsettled and represented the “American Dream” of freedom and new opportunities) because of United States imperialism, they annexed the Hawaiian Islands, Cuba, Puerto Rico and thanks to President Roosevelt, the Panama Canal Zone. Industrial enterprises developed quickly and immigrant proletariat, black people, ex slave, coming from the southern States or from central and eastern Europe. After World War I the USA choose isolationism refusing a document of President Wilson in favour of the League of Nations, and this desire for isolationism also led to a very restrictive Immigration Act in 1924.
Traditionalist Americans, called WASP (White Anglo-Saxon Protestants) wanted to control social and political behavior according to a model of white virtues. Twenty age, a period also called “Jazz period” saw an increased freedom for women and there was a low, Prohibition, which forbidding the sale of liquors.
There were new technologies as the telephone, electricity, and for example the radio which made new kind of popular culture, and there was the development of the Hollywood industry. The most important advance in technology was the diffusion of automobile which tanks to Ford’s use of assembly-line technique, was cheaply. In 1929 during Hoover’s presidency there was a crash in the American stock market, Wall Street Creash, that leaded to a Great Depression in which there was poorness, people without a hob in bad conditions.
In 1932 with the new election of President Roosevelt there was a period of liberal reforms, called the New Deal, which helped the consequences of Great Depression even if only during World War II returned prosperity, because there were the rearmament and wealth for industry. In 1939 the war broke out and USA remained neutral sending weapons and materials to European countries against Germany but after Japan’s attack to Pearl Harbour in 1941 there was the American intervention against Japan, Germany and Italy. The two generals leading the American forces were Eisenhower in the West and MacArthur in the East. Roosevelt, Stalin and Churchill met at Yalta conference, decided the division of Germany in West and east, the balance of power between Western and Eastern Europe, and created the United Nations Organization. Germany surrendered and Roosevelt died so the new president was Truman that decided to drop the two atomic bombs on Hiroshima and Nagasaki. So Japan surrendered in 1945.