- May 7, 1915. The British steamship Lusitania is sunk without warning off the coast of Ireland by a German submarine. 1,198 drowned, including 114 Americans. American indignation over the sinking led to U.S. entry into WWI against Germany in 1917.
- 1916. First U.S. troops are sent to Europe because of the escalating conflict that was to be known as the Great War (WWI). Troops did not officially participate in battle until after the United States declared war in 1917.
- 1916. Jones Act restates U.S. intention to grant independence to the Philippine Islands once a stable government is formed.
- April 4, 1917. President Wilson calls a specialsession of Congress to declare war on Germany. The Senate votes 82-6 and the House votes 373-50 in favor of war.
- 1917. Brazil declares war on Germany.
- 1917. The Russian Revolution is successful in overthrowing the Czar and instituting a Communist state.
- 1918. Canadian women are granted the right to vote.
- 1918. World War I ends on November 11th.
- July 10, 1919. The Treaty of Versailles, including the League of Nations covenant, is sent to the United States for ratification. Congress rejects the treaty and the U.S. never joins the League of Nations.
U.S. Politics & Government
- 1916. Woodrow Wilson is reelected President by a narrow margin over Charles Evans Hughes.
- April 2, 1916. Jeannette Rankin, a Republican from Montana, is the first woman to be elected to the House of Representatives.
- 1916. Louis Brandeis is appointed to the Supreme Court, the first Jewish person to reach that position.
- January 16, 1919. The 18th Amendment is ratified, forbidding the manufacture, sale, import or export of liquor in the United States, and beginning the period known as "Prohibition."
- 1920. The 19th Amendment is ratified, giving women the right to vote.
Companies, Inventions, Discoveries, & Technologies
- 1915. The Victor Talking Machine Co. introduces a phonograph, the Victorola. By 1919, Americans spent more on phonographs and recordings than on musical instruments, books, periodicals and sporting goods.
- January 25, 1915. First transcontinental phone call is made.
- July 27, 1915. Direct wireless service between the U.S. and Japan is established.
- October 21, 1915. The first transatlantic radio-telephone communication is made between Virginia and the Eiffel Tower in Paris.
- December 10, 1915. The One-Millionth Model T is produced by Ford.
- 1916. Electric clocks are introduced.
- 1916. The average price of a new car is $600. A Model T costs $360. There are over 3.5 million cars on the road.
- May 15, 1918. First airmail flights are started between New York City and Washington, DC.
- 1919. The Radio Corporation of American (RCA) is established.
- 1920. KDKA, in Pittsburgh, Pennsylvania, is the first commercial radio station. Its first broadcast is the presidential election results.
Humanities & the Arts, Entertainment & Sports
- 1916. Norman Rockwell begins to create cover illustrations for The Saturday Evening Post. He continues until 1963.
- 1918. Willa Cather writes My Antonia.
- 1919. Ten Days that Shook the World, by John Reed, a firsthand account of the Russian Revolution, is published.
- 1920. F. Scott Fitzgerald writes This Side of Paradise.
- 1920. Joseph "King" Oliver establishes a jazz band in Chicago and invites Louis Armstrong to join.
- 1920. Eight members of the Chicago White Sox are indicted for fixing the World Series. They are ultimately found not guilty, but are banned from baseball.
- November 14, 1915. African-American educator Booker T. Washington dies.
- 1916. Margaret Sanger opens the first birth control clinic.
- August 15, 1916. Tobacco baron James B. Duke orders the design and delivery of a private Pullman railcar. The cost was $38,050.
- 1918. The cost of living in New York City increases 17% between July 1917 and July 1918.
- 1920. The railroad industry peaks in importance. About this time other forms of transportation, particularly the automobile, begin to diminish the significance of the rail system.