In case you're similarly misled by this headline as I was, this is about making the archive specifically of "Editor & Publisher" available, not about some larger archive of the contents of American newspapers.
Google actually scanned a huge number of newspaper microfilm and microfiche back in 2010-11: https://news.google.com/newspapers
It's an amazing resource, but it's hidden away and researchers within Google have trouble accessing it even if they knew it existed. I spent months with lawyers to get access to the original files for research and at one point they told me they were going to delete it! Whaaaaa!?!
It was something like 6 PB, which seriously, to Google isn't much, but the team that "owned" the data wasn't using it and to them it was just an expense. Ugh. People don't care about history.
(Each * here representing some unknown third party getting access to your email address, phone number, blood type and sexual preferences.)
New York State funded an effort to scan, but not digitize historical newspapers, and while the microfilm is stored in the state archives, the online versions are hosted by an eccentric guy who digitizes the microfilm as a hobby. The guy puts everything online, but makes it difficult to work with in a variety of ways.
According to the site, it specifically avoids "major" periodicals:
"A Collection of Interesting, Important, and Controversial Perspectives Largely Excluded from the American Mainstream Media."