The Glass-Steagall Act was one of the most important documents in history. The act prohibited banks from selling Securities and tightened regulations of national banks to tie into the Federal Reserve System. It also established the Federal Deposit Insurance Corporation(FDIC).  The act was a diplomatic response to one of the leading causes of the depression.  This cause was the fact that banks we're lending out money to stock-investors, then failing to recieve payments back for the loans.  This caused a spike in foreclosures and forced banks into bankruptcy, which led to inflation and the stock market crash.  It, also, prevented the bank to become financially tied into the stock market.