Founding Fathers Online Archive
https://founders.archives.gov/
Extensive selection of letters and other personal correspondence of the Founding Fathers provided by the National Archive.
The Avalon Project: Documents in Law, History, and Diplomacy
This is an extensive collection of the major laws and other public policies that Zinn discusses in A People's History of the United States. Almost everything can be considered primary source, and almost every bill, amendment, or act is contextualized with other helpful resources.
https://www.zinnedproject.org/
Teaching A People's History: The Zinn Education Project
This is an extensive database...
