January 1 – The St. Petersburg-Tampa Airboat Line starts services between St. Petersburg and Tampa, Florida, becoming the world's first airline to provide scheduled regular commercial passenger services with heavier-than-air aircraft, with Anthony Jannus (the first federally licensed pilot) conveying passengers in a Benoist XIVflying boat. Abram C. Pheil, mayor of St. Petersburg, is the first airline passenger, and over 3,000 people witness the first departure.[citation needed]
April 21 – United States occupation of Veracruz: 2,300 U.S. Navy sailors and Marines from the South Atlantic fleet land in the port city of Veracruz, Mexico, which they will occupy for over 6 months. The Ypiranga incident occurs when they attempt to enforce an arms embargo against Mexico by preventing the German cargo steamer SS Ypiranga from unloading arms for the Mexican government in the port. On April 22 Mexico for the time being ends diplomatic relations with the U.S.
April 23 – The baseball stadium Weeghman Park, later known as Wrigley Field, opens in Chicago.
July 18 – The Signal Corps of the United States Army is formed, giving definite status to its air service for the first time.
August 1 – New York Stock Exchange closed due to war in Europe, where nearly all stock exchanges are already closed.
August 4 – German troops invade neutral Belgium at 8:02 AM (local time). Britain declares war on Germany for this violation of Belgian neutrality. This move effectively means a declaration of war by the whole British Commonwealth and Empire against Germany. The United States declares neutrality.
A dismissed servant kills seven people at architect Frank Lloyd Wright's studio and home, Taliesin in Wisconsin (including Wright's mistress, Mamah Borthwick), and sets it on fire.