1945-1968: Library of Congress
The entry of the United States into World War II caused vast changes in virtually every aspect of American life. Millions of men and women entered military service and saw parts of the world they would likely never have seen otherwise. The labor demands of war industries caused millions more Americans to move--largely to the Atlantic, Pacific, and Gulf coasts where most defense plants located. When World War II ended, the United States was in better economic condition than any other country in the world. Even the 300,000 combat deaths suffered by Americans paled in comparison to any other major belligerent.
See the Second Great Migration, from Wikipedia:
In the context of the 20th-century history of the United States, the Second Great Migration was the migration of more than 5 million African Americans from the South to the Northeast, Midwest and West. It began in 1940, through World War II, and lasted until 1970. It was much larger and of a different character than the first Great Migration (1916–1940), where the migrants were mainly rural farmers from the South and only came to the Northeast and Midwest.
See the Cold War, from Wikipedia:
The Cold War was a period of geopolitical tension between the United States and the Soviet Union and their respective allies, the Western Bloc and the Eastern Bloc, that started in 1947, two years after the end of World War II, and lasted until the fall of the Soviet Union in 1991.
See the Second Red Scare, from Wikipedia:
McCarthyism, also known as the Second Red Scare, was the political repression and persecution of left-wing individuals and a campaign spreading fear of communist and Soviet influence on American institutions and of Soviet espionage in the United States during the late 1940s through the 1950s. After the mid-1950s, U.S. Senator Joseph McCarthy, who had spearheaded the campaign, gradually lost his public popularity and credibility after several of his accusations were found to be false. The U.S. Supreme Court under Chief Justice Earl Warren made a series of rulings on civil and political rights that overturned several key laws and legislative directives, and helped bring an end to the Second Red Scare. Historians have suggested since the 1980s that as McCarthy's involvement was less central than that of others, a different and more accurate term should be used instead that more accurately conveys the breadth of the phenomenon, and that the term McCarthyism is, in the modern day, outdated. Ellen Schrecker has suggested that Hooverism, after FBI Head J. Edgar Hoover, is more appropriate.
Suburbanization, from Wikipedia:
Post–World War II economic expansion in the United States included a sudden boom in housing construction as developers raced to address housing shortages across the country. As veterans returned from war, their GI Bill benefits made it especially easy to buy homes in these new, cost-efficient neighborhoods, populating them quickly with young couples and new families. Racially discriminatory housing policies in many areas prevented people of color from buying homes in the new suburbs, making them largely white-dominated spaces. The nationwide mass migration of white homeowners into the suburbs became known as "white flight".
Note: This article is subject to a number of criticisms. See the "Talk" option for discussions of issues. Also, the role of the automobile needs to be addressed.