I'm sorry, but "a historical" just does not sound right to me. "A history" sounds just fine, so I guess it's the second syllable accent that makes the difference. I try not to sweat small language changes like that, though. Languages change all the time. Remember that Spanish, French, Italian, and Portugese all started off as one language (Latin) and over time, those small, continual changes made them different languages altogether. History lesson over.