World War I caused stock exchanges in Europe and the United States to close at the start of the conflict in 1914.
After Austria-Hungary declared war on Serbia on July 28, 1914, the crisis quickly expanded through Europe’s alliance system. Investors rushed to sell securities and obtain cash, while governments feared that gold and capital would leave their countries. Exchanges responded with closures, trading restrictions, and other emergency measures.
The New York Stock Exchange closed on July 31, 1914, and did not fully reopen until December 12. This was the longest closure in its history. London’s exchange also closed, and several European markets suspended trading or imposed controls.
The episode is sometimes described as a stock-market crash, although it was more accurately a coordinated market shutdown during a wartime financial emergency. The closures were intended to prevent disorderly selling and protect financial systems from sudden capital flight.