This University of Oklahoma College of Law website provides a timeline of key historical documents with direct links to each primary document. The timeline begins with pre-colonial documents and goes through to the present.
A University of California collection of primary documents on key historical time periods. There is relevant content, lesson ideas, and worksheets available to support the use of the documents in the classroom.
This website has a series of unsolved cases for students to learn about key events in American History using primary documents. Cases include the dropping of the bomb, school desegregation, the Boston Massacre, and many more.
Smithsonian's History Explorer offers hundreds of free, innovative online resources for teaching and learning American history. There are resources for K-12 teachers including lessons and activities, interactive media, and much more.