im sorry I for got to type the answer.This happened on october 29,1929 known as the black tuesday.

Answer 1

While black thursday is known as the day the stock market crashed, black tuesday was the day millions of panicked stock brokers sold over 16 million shares starting the great collapse.

Answer 2

That was the Stock Market crash and the start of the Great Depression.

This site has more details.

http://www.history.com/this-day-in-history.do?id=6212&action=tdihArticleCategory