You will have to do some research to determine the cost basis.  Even if your broker doesn't list the cost basis, they may be able to help.  The larger brokers have groups within that will research and determine cost basis for customers. The XEL website could be a good resource, as some companies investor relations section of their web page have information on stock basis.  The website BigCharts.com has good historical information, but they only go back to 1985.  See the following TuboTax Help Article for more infomation:  How do I find a stock's cost basis? 

Finally, as a last resort, if you can't determine your cost basis, you can always list it as zero, but that will result in your paying higher taxes.