The Great Depression was a worldwide economic downturn starting in most places in 1929 and ending at different times in the 1930s or early 1940s for different countries. It was the largest and most important economic depression in modern history, and is used in the 21st century as a benchmark on how far the world's economy can fall. The Great Depression originated in the United States; historians most often use as a starting date the stock market crash on October 29, 1929, known as Black Tuesday. The end of the depression in the U.S. is associated with the onset of the war economy of World War II, beginning around 1939.[1]