The Great Depression was the most severe economic downturn in the history of the industrialized world, lasting from 1929 to the late 1930s.

It began with the U.S. stock market crash on 'Black Tuesday,' October 29, 1929.

The crash was a trigger, but the underlying causes included overproduction, underconsumption, unequal distribution of wealth, and a fragile international financial system.

The crisis spread from the United States to the rest of the world as U.S. banks recalled loans and international trade collapsed.

Governments often made the crisis worse with protectionist policies, such as the Smoot-Hawley Tariff in the U.S.

The social consequences were devastating, with mass unemployment reaching as high as 25% in the United States.

Poverty, homelessness, and hunger became widespread, with shantytowns known as 'Hoovervilles' springing up in many cities.

The Depression led to a loss of faith in laissez-faire capitalism and democracy in many countries.

It was a major factor in the rise of extremist political movements, such as Nazism in Germany.

The economic crisis was only fully resolved with the massive government spending of World War II.