Being deeply interested in social media, I'm always on the lookout for freely available media to seed projects. Our very own United States Library of Congress is embarking on a project to digitize a huge number of US newspapers. Fab-u-lous!!
Then good old US copyright rears its ugly head. It's not so much that there the materials might be copyrighted, it's that you can't know and can't find out. Until you make some money and the vultures start to swarm.
Anyhoo, the initial seed for the project is "Stars and Stripes", an old wartime US government publication. I have to imagine that's in the public domain.
Hat tip to Waxy