Somehow I thought it was Avram Davison who wrote
The Tsaddik of the Seven Wonders (and I won't tell you the trouble I had discovering which Anglicization of 'tsaddik' was used in that work.) Possibly because I read it when I was reading Davison, more likely for the same reason people at cons think
nojojojo is Nalo Hopkinson. (wince) But anyway, now I know it was Isidore Haiblum, and that he writes mysteries as well.
And
here is a list of AU historical fantasies, some of which I may even have read.