U.S. History: 1877-2008 By Mari_ Period: 1776 to 1860 Early American History Period: 1929 to 1939 Great Depression Period: 1939 to 1945 World War II 1945 United Nations formed Period: 1945 to 1960 Early Cold War https://docs.google.com/document/d/1u-o20JvsQe-e8BnCPlCyA_bIiGD0gblF6Tzgfc7__qw/edit?usp=sharing 1947 22nd Amendment prohibits anyone who has been elected president twice from being elected again 1947 Truman Doctrine U.S. policy that gave military and economic aid to countries threatened by communism 1948 Berlin Airlift 1948 Marshall Plan a program to help European countries rebuild after World War II 1949 NATO established 1950 Korean War Period: 1950 to 1970 Civil Rights Era 1951 Rosenbergs trial 1952 First H-Bomb detonated by the United States Period: 1954 to 1976 Vietnam War 1955 Jonas Salk invents the Polio Vaccine 1957 USSR launches Sputnik Period: 1970 to 1991 End of the Cold War Period: 1990 to 2008 1990s-21st Century