Legal briefs often cite to the Congressional Record, which contains a record of debates and proceedings before the Senate and the House of Representatives. However, the Congressional Record has not always been around, and speeches and committee hearing transcripts from Congressional sessions earlier than 1873 will not be found in the Congressional Record.
From 1789 to 1824 debates before both Houses of Congress were published in the Annals of Congress. The Annals of Congress can be found on the web site of the Library of Congress here. The Annals are fully text searchable.
A record of Congressional proceedings from 1824 through 1837 is contained in the Register of Debates in Congress, which is also available on the Library of Congress web site.
The Congressional Globe was used for the publication of votes, roll calls, debates, and all other Congressional records between 1837 and 1873. Hein Online also has searchable images of these predecessors to the modern Congressional Record. See: https://heinonline.org/HOL/Index?index=congrec/conglob&collection=congrec