Why did the american economy collapse in 1929? explain the role of the primary factors, and be sure to note the role of government policy in creating the "boom" of the 1920s and the "bust" of 1929 and the great depression in general?

The Great Depression was a period of unprecedented decline in economic activity. It is generally agreed to have occurred between 1929 and 1939. Although parts of the economy had begun to recover by 1936, high unemployment persisted until the Second World War.
The 1920s witnessed an economic boom in the US (typified by Ford Motor cars, which made a car within the grasp of ordinary workers for the first time). Industrial output expanded very rapidly. Sales were often promoted through buying on credit. However, by early 1929, the steam had gone out of the economy and output was beginning to fall.The stock market had boomed to record levels. Price to earning ratios were above historical averages.The US Agricultural sector had been in recession for many more yearsThe UK economy had been experiencing deflation and high unemployment for much of the 1920s. This was mainly due to the cost of the first world war and attempting to rejoin the Gold standard at a pre world war 1 rate. This meant Sterling was overvalued causing lower exports and slower growth. The US tried to help the UK stay in the gold standard. That meant inflating the US economy, which contributed to the credit boom of the 1920s. 
During September and October a few firms posted disappointing results causing share prices to fall. On October 28th (Black Monday), the decline in prices turned into a crash has share prices fell 13%. Panic spread throughout the stock exchange as people sought to unload their shares. On Tuesday there was another collapse in prices known as 'Black Tuesday'. Although shares recovered a little in 1930, confidence had evaporated and problems spread to the rest of the financial system. Share prices would fall even more in 1932 as the depression deepened. By 1932, The stock market fell 89% from its September 1929 peak. It was at a level not seen since the nineteenth century.
Falling share prices caused a collapse in confidence and consumer wealth. Spending fell and the decline in confidence precipitated a desire for savers to withdraw money from their banks.