Solution 1:

Indeed, you are correct.

In certain accents, history, hotel, etc. are pronounced with an h sound. In those accents, a should be used. In other accents, such as my own, it is pronounced without an h sound, and therefore starts with a vowel. In that accent, it would be correct for one to say an.

Queen Elizabeth II is one such person who could correctly say an historic event. President Obama is one such person who could correctly say a historic event.

In writing, it doesn't really matter which one is used.

Solution 2:

The point of the word an is to avoid the awkward silent pause between words when saying something like "a apple." So, you should put an before any word that begins with a vowel sound, not just a vowel letter.

The good news is that you just need to do whatever makes sense when talking:

  • a historian
  • an honor
  • a xylophone
  • an X-ray
  • a user (begins with y sound)
  • an umbrella
  • a one-eyed pirate (begins with w sound)
  • an owl

Solution 3:

It is a traditional rule of English that an can be used before words that begin with an H sound if the first syllable of that word is not stressed. Indeed, some traditionalists would say it must be used before such words. Since the first syllable of historic is unstressed, it is acceptable to use an before it.

In the Corpus of Contemporary American English, there are 1591 incidences of “a historic” and 428 incidences of “an historic”, showing that usage of an before such words is dying out.

Solution 4:

Holy Moly (Or Oly Moly):

Google books ngram viewer for "a historic" and "an historic"

an historic,a historic