In Toronto, insulin isolated by Frederick Banting's team is first injected into a diabetic patient, turning a fatal disease into a manageable one.
The Nineteenth Amendment is ratified, prohibiting denial of the right to vote on the basis of sex in the United States.
The US Congress declares war on the German Empire, bringing the United States into World War I on the Allied side.
Charles Lindbergh flies solo and nonstop from New York to Paris in the Spirit of St. Louis.
The Jazz Singer, the first feature-length film with synchronised dialogue, premieres in New York, launching the era of talking pictures.
Edwin Hubble publishes the relation between galaxies' distances and recession velocities, evidence that the universe is expanding.
Martin Luther King Jr., leader of the American civil rights movement, is born in Atlanta, Georgia.