Did you know that the first televised congressional hearing was in 1948? The Senate Committee on Armed Services was the first committee to broadcast a hearing, followed by the House Un-American Activities Committee (see CRS report).
However, even though there were these few early broadcasts, the practice of filming wasn't formalized until the Legislative Reorganization Act of 1970 (PL 91-510). The Act allowed hearings to be filmed, but didn't require it -- and certainly not all hearings were recorded.
Today between the House Recording Studio, the Senate Recording Studio, and C-SPAN it's easy to watch live footage of the House and the Senate in session. Congressional committees frequently stream hearings and business meetings. And YouTube has a House Hub and a Senate Hub to bring together channels from individual member offices.
The Center for Legislative Archives is regularly asked for audio and video clips of congressional hearings. Unfortunately, copies of footage from C-SPAN and the news media very rarely end up in the official records of congressional committees.
We usually recommend researchers check with C-SPAN and other film and television archival repositories -- such as the UCLA Film & Television Archive or Vanderbilt University's Television New Archive, with the network archives -- like the NBC Universal Archive, or with library collections -- such as the television collections of the Library of Congress.
One exception are our holdings from the Senate Recording Studio from the 108th to 111th Congresses. Information on these records is available through the National Archives Catalog. You can reach us with further questions at firstname.lastname@example.org.
Also, a more general search of the National Archives Catalog will show other hearing videos in the holdings of the National Archives. After a Catalog search, look to the menu down the left side of the page. Under 'Refine By: Type of Materials', select 'Sound Recordings' and 'Moving Pictures' -- this will narrow your search results to audiovisual materials.
For more background on video recordings of the U.S. House of Representatives and the U.S. Senate, see the Congressional Research Service report: Video Broadcasting of Congressional Proceedings (April 2017).
The Smithsonian Magazine also has an article on the topic: "How Watching Congressional Hearings Became an American Pastime" (June 8, 2017).