From a JSTOR Announcement:
On September 6, 2011, we announced that we are making journal content in JSTOR published prior to 1923 in the United States and prior to 1870 elsewhere freely available to anyone, anywhere in the world. This “Early Journal Content” includes discourse and scholarship in the arts and humanities, economics and politics, and in mathematics and other sciences. It includes nearly 500,000 articles from more than 200 journals. This represents 6% of the content on JSTOR.
While JSTOR currently provides access to scholarly content to people through a growing network of more than 7,000 institutions in 153 countries, we also know there are independent scholars and other people that we are still not reaching in this way. Making the Early Journal Content freely available is a first step in a larger effort to provide more access options to the content on JSTOR for these individuals.
The Early Journal Content will be released on a rolling basis beginning today. A quick tutorial about how to access this content is also available.
See Also: JSTOR Early Content FAQ
See Also: Full Text of A Letter Sent to Publishing Partners and Libraries by Laura Brown: JSTOR–Free Access to Early Journal Content and Serving “Unaffiliated” Users
I realize that some people may speculate that making the Early Journal Content free to the public today is a direct response to widely-publicized events over the summer involving an individual who was indicted for downloading a substantial portion of content from JSTOR, allegedly for the purpose of posting it to file sharing sites. While we had been working on releasing the pre-1923/pre-1870 content before the incident took place, it would be inaccurate to say that these events have had no impact on our planning. We considered whether to delay or accelerate this action, largely out of concern that people might draw incorrect conclusions about our motivations. In the end, we decided to press ahead with our plans to make the Early Journal Content available, which we believe is in the best interest of our library and publisher partners, and students, scholars, and researchers everywhere.