The Constitution is the primary source of federal law. Over time, much of the common law has become codified in statutes, which have primacy over precedent set by court cases.
Legislation is issued in 3 intervals. First as slip laws (cited by public number), then as authoritative session laws arranged chronologically in the Statutes at Large, and finally arranged by subject in the U.S. Code.
When researching legislative history (more on sources of legislative history), it is worth noting that committee reports are more persuasive than Congressional debates.
All current legislation is arranged by subject in the United States Code.
Many free websites and subscription databases provide legislative materials including legislative history, Congressional materials, bills, statutes, and the U.S. Code.