NewspaperCat is a catalog of digitized newspapers available online, it has a lot of rinkydink small town papers from public libraries and stuff like that, which may or may not be good for your needs. Try browsing by state. The Google Newspaper Archives are also pretty good. 20s-30s is a good period for having a fair amount of digitized newspapers available. For bigger major newspapers those are usually going to be library subscription products and your best best is to get thee to a library - either a big public library in a major city, or academic libraries in state schools are almost always open to the public and provide access to their subscription digital products to visitors on site.

Otherwise maybe shoot /u/anoldhope a PM, he studies the this topic. Best of luck with your research! :)