Generally, legislative histories are not already written. They must be compiled by the researcher. However, there are published legislative histories available in books as well as in journal articles. There is also a legislative history library of compiled legislative histories available on Heinonline.
Black's Law Dictionary defines legislative history as "the background and events leading to the enactment of a statute, including hearings, committee reports, and floor debates."
One of the primary purposes researchers investigate the legislative history of a particular piece of legislation: "Legislative history is sometimes recorded so that it can later be used to aid in interpreting the statute."