Which exchange’s 1873 collapse is commonly seen as the opening shock of the Long Depression?

The Vienna Stock Exchange’s collapse in 1873 is commonly seen as the opening shock of the Long Depression.

A speculative boom in Austria-Hungary ended with the Vienna stock-market crash on May 9, 1873, known as Black Friday in Vienna. Share prices had risen rapidly amid easy credit and enthusiasm surrounding industrial expansion. When confidence broke, bank and company failures spread through financial markets.

The panic soon affected Germany and the United States, where the failure of Jay Cooke & Company helped trigger a major crisis later in 1873. The resulting worldwide downturn is often called the Long Depression, although its timing and severity varied by country. It lasted much longer than the 1930s Great Depression in many historical accounts. The Vienna crash was a starting shock, not the only cause of the broader depression.