It sometimes seems like you can find anything you could possibly want to know on the internet. This is not the case as I discovered a few days ago when I tried to find the stock trading symbol for Standard Oil of Indiana. Perhaps this information is actually on the internet somewhere but I was unable to find it.
On a related note this site allows you to easily look up stock prices going back to January 1, 1970. But only if the company is still in existence. If you want historical prices for a company like Standard Oil of Indiana which first changed its name to Amoco and then was bought by British Petroleum you are apparently out of luck.
This sort of memory loss can cause something called survivorship bias . If you compute average returns over a period of time only for stocks (or mutual funds) still in existence at the end of the period you may obtain a misleadingly high result as you will omit the results for all the companies that disappeared (often wiping out their shareholders in the process) during the period.