Across the Generations: Exploring U.S. History Through Family Papers is a digital collection available on The Smith College Libraries website.
The introduction to this collection makes it clear that it doesn't matter if your family isn't represented in a manuscript collection it still can have importance to your research. "Family papers contain a wealth of information. Most obviously, the history of a particular family can be learned by examining the records a family leaves behind. At the same time, the larger trends and events can be traced within the records of one family."
Documents in this collection have been divided into themes that include Family Life, Social Awareness and Reform, Arts and Leisure and Work.