For what it's worth, I am in history and about to finish my M.A. - after 4 semesters, I have never had a female professor in grad school... I do know, however, that there are a couple female professors in my department - I just haven't had either of them for a class. And as far as students, my department is about 3:1 male. I was surprised at first, but not anymore. Maybe it's just my department, or maybe it's the field of graduate-level history? I don't know...