May 9, 1873, is associated with the Vienna Stock Exchange crash that helped begin the Panic of 1873.
The date is known in German-speaking historical writing as the Gründerkrach, or founders' crash. Speculative investment had expanded during an economic boom, especially in railways, construction, and property. When confidence broke, share prices collapsed in Vienna.
The shock spread beyond Austria-Hungary through interconnected banks and financial markets. The United States experienced its own major panic later that year, after the failure of the banking firm Jay Cooke & Company in September.
The Panic of 1873 ushered in a long period of economic weakness often called the Long Depression. Terminology varies by country, so the Vienna event and the later American panic are sometimes treated as separate stages of the same international crisis.