Last week the Library of Congress announced new additions to their online resources that make finding these materials even easier. The Library of Congress updated their Search by Standard tool to now include Common Core standards specific to each state and allow teachers to sort between ELA and Social Studies materials. If you teach either of these content areas, the Library of Congress is going to be quite handy. A quick search for California 8th grade Social Studies yielded hundreds of resources including primary source sets, lesson plans, and activities broken down by standard.
If you find these materials handy consider subscribing the the Teaching with the Library of Congress blog. This site regularly posts great ideas for using primary source materials in the classroom and periodically curates them for you, especially for upcoming events such as Veterans Day.