The federal Fair Credit Reporting Act (FCRA) requires each of the nationwide consumer reporting companies to provide you with a free copy of your credit report, at your request, once every 12 months.
http://www.ftc.gov/bcp/conline/pubs/credit/freereports.htm
This web site tells all about the program and how to request the reports.
Another useful site:
https://www.annualcreditreport.com/cra/index.jsp