1914 – World War I begins after the assassination of Archduke Franz Ferdinand, heir to the Austro-Hungarian throne. However, the causes lie deep. For many years, partly as a result of increased populations and the discontent with industrialized society, tensions in Europe had been rising, and with them, nationalism, military forces, and national alliances. When it was discovered that the Archduke's assassin was a member of the Black Hand, a terrorist group that vowed to unite Bosnia and Serbia as a single nation, Austria-Hungary mobilized military forces to punish the Serbs. Russia decided to help the Serbs, and in response, Germany joined Austria-Hungary, and then declared war on Russia and France. A domino effect was set in motion: Great Britain, Japan, Romania, and later Italy to the side of "Allies" France and Russia, and Bulgaria and Turkey to the side of Germany and Austria-Hungary. President Wilson declared America's neutrality.

1914 - 1920 – In what became known as the "Great Migration," nearly half a million Southern blacks migrated to the North for factory jobs and to escape racial prejudice.

1915 – A German submarine torpedoes the Lusitania, a British passenger ship, killing almost twelve hundred people, 128 of them Americans. Later, it was revealed that the ship was carrying munitions. President Wilson demanded that Germany agree not to launch any similar attacks. After a delay, Germany agreed.

Wilson develops a policy of "preparedness." To prepare for peace, the President toured the country promoting his policy. He then pressed Congress to double the army, increase the National Guard, and build the largest navy in the world.

1916 – President Wilson reelected by a slim margin, 23 electoral votes and 600,000 popular votes. Wilson campaigned on the promise of continued peace and prosperity. Many voters felt that Charles Evan Hughes was more likely to lead the U.S. into war.

1917 – Germany resumes unrestricted submarine warfare. Germany began firing on merchant ships after hearing that such vessels would be carrying munitions. When Americans were killed by a German attack on the French steamer Sussex, Wilson demanded a halt to such attacks and Germany acquiesced.

Zimmerman telegram released. The British turned over to Wilson an intercepted telegram from Arthur Zimmerman, German foreign minister, to the Mexican government. If the United States and Germany were to go to war, Zimmerman proposed that Mexico ally itself with Germany. After the war, Germany would reward Mexico with Texas and parts of the Southwest. The telegram was widely published in an effort to build popular opinion in favor of America's entry into the war.

U.S. enters World War I. By 1917, the war had become a stalemate. However, when Russia collapsed from within, a key ally was lost and morale in the Allied troops was driven lower. These factors, along with the Zimmerman telegram and the German sinking of the Algonquin, an American merchant ship, led the U.S. to declare war on Germany. The American presence tipped the balance immediately.

The Selective Service Act assembles the necessary American fighting force.

Russian Revolution breaks out. The Bolsheviks topple Czar Nicholas II. The new communist government, led by I. V. Lenin, withdraws from the war.

1918 – The Sedition Act makes illegal any public expression of opposition to the war. Under the law, Eugene Debs, leader of the Socialist Party, was sentenced to ten years in prison. President Warren G. Harding granted him a pardon in 1921.

Wilson's Fourteen Points for peace. In January, Wilson appeared before Congress to outline his Fourteen Points. Points 1-8 concerned the adjustment of European boundaries and the establishment of new nations – these points reflected Wilson's belief in the right of self-determination. Points 9-13 were intended to maintain peace (open seas, open covenants instead of secret treaties, arms reductions, free trade, and impartial arbitration of colonial claims). Point 14 was a proposal for a "League of Nations." However, there were problems with the Fourteen Points. For instance, France and England, who suffered tremendous casualties in the war, did not intend to be so generous in victory.

On November 11, an armistice ends World War I.

The Paris Peace Conference officially settles terms of the armistice. While Wilson's Fourteen Points were not completely accepted and his idealism subverted by French and English imperialism, Wilson was pleased that all agreed to establish a League of Nations. At home, however, the League fared worse. The Senate failed to ratify the Treaty of Versailles and expressed particular concern that the League would subject America to the will of other countries. The U.S. negotiated a separate peace from the Allies, one that was not ratified by Congress until 1921.

1919 – Race riot erupts in Chicago. While swimming, a black teenager drifted over to a whites only Lake Michigan beach, where he was stoned to death. Blacks retaliated and whites responded. After over a week of violence, thirty-eight people were killed, 537 were injured, and over one thousand were left homeless. The Chicago riot was the worse of several race riots in American cities during the "red-summer" of 1919.

Over 3,600 strikes involving four million workers occur as a result of high inflation, a twelve-hour workday, and employers' rescinding war-time benefits.

Steel strike begins in September 1919 when 350,000 steelworkers in several Midwestern cities demand an eight-hour workday. The strike climaxed in a riot in Gary, Indiana in which eighteen strikers were killed. With non-union workers keeping most plants operating and public opinion against the strikers, the strike collapsed in January.

1920 – The Nineteenth Amendment grants women the right to vote.

Prohibition begins after the Eighteenth Amendment is ratified by every state but Connecticut and Rhode Island.

Palmer raids and Red Scare. Concerns about Communism spread when the Soviet government announced the formation of the Communist International (or Comintern), intended to promote the communist cause. Attorney General A. Mitchell Palmer, whose home had been damaged by a bomb thought by many to be part of a communist conspiracy, raided alleged radical centers and arrested some 6,000 people. The Palmer Raids were intended to uncover weapons and explosives – they netted three pistols. Most of those arrested were released.

Warren G. Harding elected president in a landslide victory over James M. Cox.

Eugene O'Neill's Beyond the Horizon opens on Broadway.

1921 – Congress establishes a quota system by which annual immigration could not exceed 3 per cent of the number of persons of that nationality who had been in the United States in 1910. Immigration fell from 800,000 to 300,000 in a single year.

1922 – Motion Picture Association founded.

T. S. Eliot publishes The Waste Land.

1923 – Harding dies suddenly while on a speaking tour in San Francisco. Calvin Coolidge becomes president.

Scandals revealed involving members of the Harding administration. Harding may have been unaware of the scandals, of which Teapot Dome was the most sensational. Harding's Secretary of the Interior, Albert B. Fall, convinced Harding to transfer Teapot Dome, Wyoming, and Elk Hills, California, to the control of his department. Fall then leased the land to two wealthy businessman and Fall received almost $500,000 in "loans" to help him with his financial troubles. The Secretary was convicted and sentenced to a year in prison.

Ku Klux Klan membership rises to a reported four million. The old Klan, formed during Reconstruction, had died in the 1870 by a group of white Southerners who met on Stone Mountain, GA. After WW I, the Klan continued to intimidate blacks, but now attacked Catholics, Jews and foreigners as well.

Time magazine founded.

1924 – The National Origins Act further restricted immigration than the legislation of 1921. No immigrants from the Far East would be permitted entry to the United States. (This restriction was aimed at Japan since Chinese immigration was already illegal.) The law reduced the quota of immigrants from Europe from 3 to 2 per cent to be based not on the 1910 census, but on the 1890 census when there were fewer southern and eastern Europeans in the U.S.

Calvin Coolidge was elected president in a landslide.

1925 – John T. Scopes convicted of teaching evolution in Tennessee. The judge ruled that scientists could not be used to defend evolution, since all their statements and theories must be considered "hearsay" because they were not present at the Creation.

F. Scott Fitzgerald publishes The Great Gatsby.

1927 – Sacco and Vanzetti executed. In May of 1920, two Italian immigrants, Nicola Sacco and Bartolomeo Vanzetti were charged with murder in the death of a paymaster in Braintree, Massachusetts. Many felt they were innocent and only convicted because of their confessed anarchist beliefs and the lingering Red Scare climate of the country. Although public support grew for the pair, a new trial was denied. They died in the electric chair proclaiming their innocence until the end.

Charles Lindberg flies the first successful solo transatlantic flight. Previously, eight other flyers had died in the attempt.

The Jazz Singer, the first sound motion picture, is released.

1928 – Herbert Hoover defeats Alfred E. Smith in the presidential election.

Kellogg-Briand Pact, signed by all the major nations except the Soviet Union, prohibits war. Named for U.S. Secretary of State Frank Kellogg and French foreign minister Aristide Briand, the Pact was ineffective as there was no means of enforcement.

1929 – Stock Market Crashes. On October 21 and 24, stock prices plummeted, but recovered temporarily each time. But on "Black Tuesday," stock prices plunged and no recovery ensued. At their peak in 1929, stock prices had been worth $87 billion, but by 1933, they bottomed out at $18 billion. The stock market crash was not the cause of the Great Depression, but a strong indication of an impending crisis.

There were several causes of the Great Depression:

William Faulkner publishes The Sound and the Fury.