A ticker symbol is a short abbreviation used to uniquely identify publicly traded shares of a particular company. You can find these in many of the business databases or you can use free financial websites such as Yahoo! Finance.
These sources have stock prices only for companies with stock that is currently being traded.
Another nice free web site for getting stock prices and much more.
Historic Stock Prices
Use these to find the daily stock price for companies that no longer have actively traded stock (e.g. companies that have merged, gone out of business, etc.). Most recent years are located in 2 North Reference. Prior years in Lower Level.
Daily Stock Price Record American Stock Exchange - HG 4915 I22
Daily Stock Price Record New York Stock Exchange - HG 4915 I23