Legislative History is the term used to refer to documents generated by a legislative body during the process of passing a bill.  It includes bill text, hearings, congressional debates, committee reports, presidential messages, and other documents. Legislative history is used to help interpret statutes if the meaning is ambiguous. The information gathered is usually used to determine the answer to the question: what was the intent of the congress?

If you want to research a new statute, a bill that has been introduced into Congress but not yet passed, or find background information about an existing statute, you may need to do legislative history research.

Each stage in the legislative process generates documents that may be useful in determining congressional intent. For example, see the following diagram on the federal congressional lawmaking process from Westlaw.  Note that on the web you can click on this web page and it will take you to the Westlaw database which corresponds to that stage of the congressional lawmaking process (a subscription to Westlaw is required to search these databases).

You can also search Thomas, the Library of Congress Legislative Information Service for legislative history documents, particularly for more recent statutes.