"I think 'an historical' sounds prissy and affected. I would put the phrase in the mouth of a prissy, pretentious prescriptivist."
I refuse to take umbrage at this statement, having matured a few decades since I titled my senior thesis,
"An Historical Review of the Theories of Phototropism." Sounded good at the time (1960) and flew through the reviewers at the University of California with no requests for revision. Of course, the reviewers were all of a scientific bent and easily intimidated by what they might have suspected was an arcane rule of grammar and spelling.