Congress.gov is the official website for U.S. federal legislative information. It is also free.
Using advanced search on Congress.gov, you can enter your public law number, and select the relevant congressional session. For example, in the circled area, you could enter "101PL549" (101st Congress, 549th enacted bill) and narrow your search to information from Congressional sessions from 1973 -2022. This is the Public Law Number for the Clean Air Act Amendments of 1990.
You can receive fairly comprehensive results, including a summary, bill text, actions on the bill, amendments to the bill, cosponsors, committees, and references to congressional reports.
Committee Reports are often seen as the most important document in legislative history. The House, Senate, and Joint Conference Committees can all issue reports, which may analyze the intent of the proposed legislation and the committee's rationale for recommending a bill.
Committee reports are available on Congress.gov from 1995 (104th Congress) forward. You may search for Committee Reports using the drop down menu available on Congress.gov.
Free access to historical committee reports requires more effort. Selected materials appear in Century of Lawmaking (1774-1875). For more information, the Library of Congress has a guide devoted to finding historic Congressional Committee Reports.