JSTOR announced that they provide free access to 218 journals with content prior to 1923 in the United States and prior to 1870 elsewhere. This involves about 500.000 articles.
You can search all free available JSTOR content via a dedicated search page.
For libraries who are using a link resolver it is even easier. They can just select the JSTOR Free Early Journal Content in the knowlegde base they are using.
JSTOR Free Journal content in the Serials Solutions knowledge base
By a simple mouse click they can add all 218 titles to their collection and offer integrates access to their patrons.