I recently published an article - Search 40 Million Historic U.S. Newspaper Pages for Free!, which listed over 430 links from 37 states and a grand total of over 40 million newspaper pages available to be searched for free. Those collections were made available by the cooperation between many local and county libraries and historical societies in conjunction with the Advantage Preservation Company.
My friend, Brian Olmstead from Denver, Colorado, took it a step further and included those links in a very useful custom Google Map. All of those collections are mapped in the image above.
To see it a bit better, let's look at just one state (Louisiana) and see what we have.
Everywhere you see a balloon, there is a collection available online. Having a mapped set of collections is very useful, especially when there are dozens of collections available, as in Iowa, Illinois, Ohio, New York and a few other states. It enables the researcher to see what additional newspaper collections might be available to search in a location near the search subject person's residence, or birth, or death place or any other event for that person.
If we click on a ballon, it brings up the url for the collection in addition to other useful info:
I chose the Vernon Parish Library in western Louisiana and you can see the information now available - name of the Library that provided the newspapers to be digitized and included in the online collection, the url for the online collection so that one can search it, and contact information for the library, as well as a photo or two.
To get access to the map, click on https://drive.google.com/open?id=11twsadf5ymMfF22gMH8n-NCskIg&usp=sharing
Thanks Brian, this is a terrific and very useful search aid that you have created!