Where CUSIP Comes From
The Committee on Uniform Securities Identification Procedures, or CUSIP, was set up in the 1960s to ease stock transactions. The CUSIP system is the property of the American Bankers Association and is maintained by Standard & Poor's. For access to the complete list of numbers, you need paid access to a CUSIP database. However, you can look up individual companies' numbers for free elsewhere.
Looking up Individual Stocks
A few financial information sites allow you to enter a CUSIP number to identify which stock it belongs to. These include Fidelity Investments and Quantum Online. Type the number into the search box, select "CUSIP Number" from the drop-down menu, then hit "Search." At Quantum Online, you can also find out the CUSIP number for an individual stock. Enter the stock's ticker symbol, select "By Ticker Symbol" from the menu, and click "Search." The CUSIP number appears on the stock's information page.