"laissez-faire" approach to the economy, economics homework help

Up until the 1930s, the government took a "laissez-faire" approach to the economy. What changed and who was the main influence for this change? In what situations would government intervention into the market place warrant price controls? Please provide a couple of examples in your response. As an additional item who has encountered the price increase due to the minimum wage increase here in Michigan? How many were surprised at the increase in price on regular items that you purchase (i.e. the dollar menu or lack thereof)?