Tracing Federal Legislation

The United States Code

"...a consolidation and codification by subject matter of the general and permanent laws of the United States. It is prepared by the Office of the Law Revision Counsel of the United States House of Representatives."

also available: 1994- via govinfo.gov
                        1925 edition and supplements to 1988 edition and supplements via the Library of Congress

In the Library. 1st floor, Reference,  KF62 2018 edition and supplements