The New York Stock Exchange closed for four months on 31 July 1914 after the outbreak of World War I created extreme financial uncertainty.
European markets were already under severe pressure as investors tried to liquidate securities and obtain cash. The NYSE closed to prevent disorderly selling and to limit the export of gold. It remained shut until 12 December 1914, making this one of the longest closures in its history.
The closure was not itself a conventional one-day stock-market crash. It was an emergency response to wartime disruption, currency pressure, and the breakdown of normal international finance. When trading resumed, prices rose in many securities, partly because the exchange had suppressed forced selling and because wartime demand changed economic expectations.
The date is sometimes confused with 28 July, when Austria-Hungary declared war on Serbia, or 4 August, when Britain declared war on Germany. The exchange closure began before those later milestones.