Remember, the first rule of legal research is "Don't reinvent the wheel!" If someone else has already compiled a legislative history, USE IT! It will save you hours of research and lots of headaches. Although compilations don't exist for every bill, there are more and more available each day. And, even if you cannot find a complete history, a partial history will give you a great start!
There are a few different types of compiled legislative histories out there. They are:
1) Indexes to published or compiled texts. These are lists of all of the legislative histories on a topic, law, or bill. They will not give you substantive information or citations, but they will direct to a publication that can provide you with that information. Examples of an index are Sources of Compiled Legistlative Histories by Nancy Johnson (also on HeinOnline), and Federal Legislative Histories by Bernard D. Reams.
2) Compiled lists of legislative documents. These are lists of the citations of the legislative documents. Many of the online legislative histories will have links to the documents contained on their database. Examples of a compiled list are ProQuest Legislative Histories, CIS Legislative Index, and the Library of Congress's website.
3) Complete published sources. These are often difficult to find, but they contain duplications of all of the legislative documents for a bill or law. Many times they also contain commentary about the formation of the law. Complete published sources can be found using an index. HeinOnline does contain complete published sources for limited laws in the U.S. Federal Legislative Title Collection.