Quote from stevegee58:
Here is an academic article about the WW I closure published in 2005. Warning: it's 30 pages long.
Here's a snippet:
"Exchange officials maintained that the threat of
European liquidation of US securities justified a suspension in trading as a
circuit-breaker. However, the exchange remained shuttered for more than four
months, from July 31, 1914 to December 12, 1914. Closing the Exchange for
more than four months would be unthinkable today. It was also unthinkable in
1914."