History
https://www.khanacademy.org/humanities/world-history
http://eyewitnesstohistory.com/
https://www.loc.gov/collections/?fa=subject:american+history
https://www.loc.gov/collections/index/subject/
https://memory.loc.gov/ammem/browse/updatedList.html
https://sourcebooks.fordham.edu/index.asp