Context: The US economy was in a boom after World War I, the domestic market was hot, and Europe was demanding manufactured goods.
Causes: In order to make more money, companies have created an overproduction of goods and services. To do this, they sought credit from the banks - which expanded their credit portfolios in a wild way. However, Europe has recovered economically and drastically reduced demand for American products.
Consequence: Domestic demand was not sufficient for the outflow of products. Inventories increased considerably, the businessmen lost the conditions to pay their loans to the banks and the financial system collapsed. Unemployment rose and the economy went into recession.