Here are a few good places to start your research-
Provides free online full text access to official and final versions of U.S. Federal Government publications from the Executive, Legislative, and Judicial branches, the Congressional Record, Federal Register, United States Code (USCS) and more. 1793 to present.
Decisions and case law from all state and federal courts, statutes, federal regulations, law review and legal journal articles. 1789-present.
Reports on a wide range of topics, with overviews, background and timeline of a topic, assessment of the current situation, tables and maps, pro/con statements from opposing positions. 1923 to present.