United States population: 103,500,000.
More than half of the country's 48 states prohibit the sale of alcohol.
Daylight Savings Time and time zones are introduced.
Regular airmail service between New York City and Washington, D.C. is established. A flight from Chicago to New York takes 10 hours, five minutes.
The New York Times begins home delivery. In New York City, the first three-colored traffic light is introduced. Also making their first appearances are granulated laundry soap, Raggedy Ann dolls and Ripley's Believe It or Not!
On April 22, 1918, Manfred von Richthofen, the infamous "Red Baron," is killed at the Battle of the Somme.
Vicente Blasco-Ibanez's The Four Horsemen of the Apocalypse is the best-selling book of the year. Other books: Willa Cather's My Antonia and Booth Tarkington's The Magnificent Ambersons. The United States Post Office burns installments of James Joyce's Ulysses, published in the "Little Review."