Your editor advises me that he does not consider it the purpose of Word Ways "to serve as watchdog over the purity of the English language," but concedes that an occasional growl might do no harm.
Let me attack, then, a practice that is widespread and in my view indefensible -- yet is perpetuated by many in the best position to serve as preceptors of good usage. I refer to using an before "historical" or "historic".
Berryman, George R.
""An Horrible Usage","
Word Ways: Vol. 8
, Article 3.
Available at: http://digitalcommons.butler.edu/wordways/vol8/iss4/3