I believe that the answer is Mesopotamia, China, Egypt, and India.
There were multiple spaces where three multiple skeletons have been uncovered in a single grave in the past. When we find mass graves of skeletons from the past, this means we've likely found a place where people have been killed.
Explanation:
Stock Market Crash of 1929 - Many believe erroneously that the stock market crash that occurred on Black Tuesday, October 29, 1929 is one and the same with the Great Depression. In fact, it was one of the major causes that led to the Great Depression.
