1900- The United States Population exceeds seventy-five million.
1900- The Gold Standard Act was passed.
1901-Theodore Roosevelt becomes President
1903- The movie "The Great Train Robbery" opened.
1903- The Ford Motor Company was formed.
1903- The Wright brothers made their first powered flight in the Wright Flyer.
1906- The Pure Food and Drug Act and Meat Inspection Act were passed.
1906- San Francisco earthquake occurred.
1908- The Ford Model T appeared on the market.
1909- William Howard Taft became President.
1909- Robert Peary claimed to have reached the North Pole.
1909- The NAACP was founded by W.E.B. Du Bois.
1911- The Supreme Court broke up Standard Oil.
1911- The First Indianapolis 500 occurred.
1912- The Titanic sank.
1912- Roosevelt was shot while campaigning for the Bull Moose Party.
1913- Woodrow Wilson became President.
1913- The Federal Reserve Act was passed.
1914- World War I Began
1914- Mother's Day was established as a national holiday.
1915- The Lusitania was sunk.
1917- The United States entered World War I.
1919- The Treaty of Versailles ended World War I.
1919- The Eighteenth Amendment to the United States Constitution was passed.
1919- Black Sox scandal occurred.
1920- The Nineteenth Amendment to the United States Constitution was passed.
1920- The first radio broardcasts were made, in Pittsburgh, Pennsylvania and Detroit, Michigan.
1920- The Volstead Act was passed.
1921- Warren Harding became President.
1923- Harding died and Calvin Coolidge succeeded him.
1927- Charles Lindbergh made the first trans-Atlantic flight.
1928- Disney's animated feature "Steamboat Willie," featuring Mickey Mouse, opened.
1928- Amelia Earhart flew solo across the Atlantic Ocean.
1929- Herbert Hoover became President.
1929- St. Valentine's Day massacre took place.
1929- Wall Street crashed and the Dow Jones Industrial Average dropped a record 68 points.
1931- The Empire State Building opened in New York City.
1932- The Bonus Army marched on Washington, D.C.
1933- Franklin Delano Roosevelt was worn in as President.
1933- Roosevelt introduced the New Deal, focusing the "3 Rs" of relief, recovery and reform.
1934- The Dust Bowl began.
1934- The FBI was established, with J. Edgar Hoover as its first director.
1937- The Golden Gate Bridge was completed in San Francisco.
1939- Poland was invaded by Nazi Germany.
1941- Attack on Pearl Harbor took place.
1942- Japanese American internment and seizure of property began per executive order 9066.
1944- Normandy landings took place.
1944- Battle of the Bulge took place.
1945- Battle of Okinawa took place.
1945- Roosevelt died and Harry S. Truman became President of the United States.
1945- Germany surrendered.
1945- Atomic bombs were dropped on Hiroshima and Nagasaki.
1945- The Nuremberg Trails began.