Major Acts of Congress (Gale Virtual Reference Library) "examines landmark pieces of legislation, explaining the historical factors that led to the proposal of each act, looking at the adoption process and assessing each act's impact on American life."
U.S. Code Service (USCS) -- Reference KF 62 1972 .L38
U.S. Code Annotated (USCA) -- Reference KF 62 .U6
Legislative Histories provides step-by-step instructions for researching the history of a public law.
Slip Laws -- current uncompiled laws
Statutes at Large (Stat.) and Public Laws (P.L.) - "Every public and private law passed by Congress is published in the Statutes at Large in order of the date it was enacted into law. The laws are arranged by Public Law number and are cited by volume and page number. Also included in the United States Statutes at Large are concurrent resolutions, proclamations by the President, proposed and ratified amendments to the Constitution, and reorganization plans. Until 1948, treaties and international agreements approved by the Senate were also published in the Statutes at Large."
U.S. Code Congressional & Administrative News (USCCAN)