Alex Wellerstein’s navigation of the Manhattan District History, 36 volumes, mostly redacted, by Gavin Hadden, general editor (father of JLH Sr)

http://blog.nuclearsecrecy.com/2014/09/05/general-groves-secret-history/

Excerpts:

The first history of the Manhattan Project that was ever published was the famous Smyth Report, which was made public just three days after the bombing of Nagasaki. But the heavily-redacted Smyth Report understandably left a lot out, even if it did give a good general overview of the work that had been done to make the bomb. Deep within the secret files of the Manhattan Project, though, was another, classified history of the atomic bomb. This was General Leslie Groves’ Manhattan District History

Groves didn’t write the thing himself, of course. Despite his reputation for micromanagement, he had his limits. Instead, the overall project was managed by an editor, Gavin Hadden, a civil employee for the Army Corps of Engineers.

 

DOE website on the Manhattan District History:

https://www.osti.gov/opennet/manhattan_district.jsp