Civil War pension files can contain a variety of information. The one for William Lake (Co.I, 49th Missouri Infantry) contains a copy of his family’s 1860 census transcription.

Too bad I had already located them in the 1860 census, but a transcription from 1915 by the Department of Commerce (who used to oversee the census) was still a neat find.

Of course the citation for the census record in the letter isn’t up to modern genealogical standards, but we will let it slide. There is adequate information there to find the original. If this letter was the only place I could find the census information, I would cite the letter.

And this transcription would be a derivative source for the census enumeration, just like any transcription.