The fortnightly book this time around is The River Witch, by Marjorie McIntyre, a tale of love and riverboats on the Missouri River in the 1850s. (It should not be confused with the book of the same name by Kimberley Brock.) This was McIntyre's debut and apparently only novel, although I think she also wrote short stories for magazines. I don't know much other than that about the author or the book. Published in 1955, it seems to be a book that's hard to get a hold of, but occasional internet reviews of it are almost all glowing, so it may well be an overlooked treasure.
This book was in my grandparents' library. I suspect it is from my granmother's side of the library, although it lacks anything to indicate for sure. It has a nice map inside the covers of "River Witch Country 1850", depicting the Missouri River from St. Joseph in Kansas to St. Louis in Illinois.