The invaluable Internet Archive has just added an archive of TV news content. So far it only goes back to 2009, but hopefully they will add older content. From the page:
I have to say, if the Internet Archive as a whole is new to you, you’re gonna be in there a while. The public domain feature film collection alone is massive, not to mention all the hours of Grateful Dead concerts, Prelinger Archive ephemera, old-fashioned pornography, ebooks, etc. etc. etc. And that doesn’t even touch anything the Wayback Machine has to offer.