I posted my ABH column on tomato gravy last week, noting that I'd post some of the emails I received, thanks to inquiries by Rebecca Lang, after press time that shed a bit more light on my quest for the dish's history.
Here's what Damon Lee Fowler, a food historian and writer in Savannah, had to say:
I would've sworn it was in Mrs. Dull, but it wasn't. HOWEVER, the recipe she gives for tomato sauce is for all intents and purposes, tomato gravy--with thickener, etc. Also, Mrs. Bryan (The Kentucky Housewife) has a tomato sauce that is essentially tomato gravy, with a butter and flour liaison, etc.
(I do know, too, that Italian-Americans often called their tomato sauce "tomato gravy" and you sometimes see that in Italian-American books, but of course it was not the same thing.)
Likewise, I would've sworn that Mrs. Hill had it in her book (1867) but I don't find it there, not even called "tomato sauce." Ronni Lundy has a lovely recipe in Butterbeans to Blackberries, but she doesn't get into the history. However, her off-hand mention of it as a "country kitchen staple" is suggestive that it might have been a very rural, farmhouse-kitchen thing that urban cookbook authors would not have written about.
I heard my grandmother talk about tomato gravy from her childhood, but I don't remember her ever making it. My mother remembers it but didn't make it, either.
I don't think it can have been peculiar to just one state, because Ronni hails from Kentucky and my family is from the Georgia/Carolina hill country around Hartwell/Anderson.
Other emails from Fowler and noted TV personality and Southern cookbook author Nathalie Dupree noted that tomato gravy had existed in the South for some time, just not with its current name. All of their digging points to tomato gravy being a rural, inland recipe, as documents of it occur only in church cookbooks from those areas, and not coastal or urban communities.