In the United States things were improving after WW1. That is until Black Tuesday.
In 1920 hundreds of people were buying stock. Some people even borrowed money to buy stock because they thought they could pay it back and have money left over (Not a good idea.)
Turned out they were wrong. Starting in 1929 a few people started selling there stock, then a few more people started selling. After a while hundreds and hundreds of people were selling their stock. Stock value plummeted almost to zero. The whole week was called the Wall Street Crash. Tuesday was the worst day in that week. $4,000,000 worth of stock was lost. Eventually this crash led to the Great Depression. This was a dark age for America.