Joshua Friedman (@joshuajfriedman) writes on Twitter:
Have you written or read anything about the relatively recent resurrection of “an historic”? My casual experience makes me think it happened around the 2008 election, but I haven’t seen data.
He’s referring to using “an” rather than “a” before words that start with a non-silent “h,” like “habitual,” “happy,” and “hotel” (but not “honest” or — in America — “herb”). Here’s the general lay of the land, from Google Ngram Viewer (which has reliable data only through 2000):
You can see “an historic” was traditionally more common in Britain (red line) than in the U.S. (orange line), but that “a historic” overtook it in both countries — in the late ’30s in America, in the late ’60s in Britain. So “an historic” counts for me as Britishism. The question is whether Joshua’s correct and it’s lately been taken up by Americans.
By the way, I chose the mid-’20s as the start of the chart for a reason. H.W. Fowler’s Modern English Usage was published in 1926, and in the very first entry, Fowler takes on this subject, writing in his inimitable way:
“A” is used before all consonants except silent h (“a history,” “an hour”); “an” was formerly used before an unaccented syllable beginning with h (“an historical work”), but now that the h in such words is pronounced the distinction has become pedantic, & “a historical” should be said and written; similarly “an humble” is now meaningless & undesirable.
And also by the way, in 1997, when Kevin Kerrane and I were choosing a subtitle for our anthology The Art of Fact, we chose A Historical Anthology of Literary Journalism, only briefly considering An Historical….
So have things changed since 2000? Contra Friedman, apparently not significantly. The News on the WEB (NOW) consists of nearly 9 billion words published on news sites between 2010 and the present. In it, “a historic” shows up 6.56 times per million words and “an historic” 1.52 times per million words, a proportion that has held steady from 2010 till now. Still, that 4-1 ratio reveals “an historic” having surprising staying power, which is probably what Joshua was observing. According to NOW, it’s used most commonly in Ireland, and least commonly — but not negligibly — in Canada and the U.S.
And here are some examples of its American use over the course of just five days recently, also taken from NOW:
notoneoffbritishisms.com 
I have wondered whether it was one of those attempts to show superiority in language by imitating French pronunciations, as in un hotel and une histoire.
I tend to say and write “an historic” as it just sounds right, but I don’t know why. I’m a Londoner and they are known for dropping their aitches but I don’t think I say “an ‘ouse” or “an ‘orse”.
I’m sure that in many cases that applies, as in ‘A policeman’s lot is not an ‘appy one’. (It actually becomes ‘a nappy one’. But you probably wouldn’t say that they have taken him to an ‘ospital or an ‘eavenly choir. Therefore, it isn’t entirely a reluctance to say our aitches. Also, I think that I remember from my childhood that ‘an ‘otel’ was ‘the correct’ way to pronounce it. Rather like the insistence on ‘hiccoughs’ instead of ‘hiccups’.
Talking of Londoners and pronunciations reminds me of the delightful Tony Weller, telling his son in court how to spell his name: “Vith a Wee, Samivel. Vith a Wee.”
I think I probably do say “an ‘otel”.
I’m a Londoner and also say an hotel, an hospital and an historic. I remember being taught in school in the ’50s that those were the correct pronunciations and written forms.
Ben, is there anything you can do to make your charts larger? I notice here – and in some recent past posts that they’re practically illegible, even on a 15-inch monitor. The Google graphs are fine.
Thanks!
I’m not sure. Let me fiddle with it. I take a screen shot of the image and WordPress doesn’t seem to let me make it bigger, only smaller.
Incidentally, your mention of the American pronunciation of “herb” reminded me of two TV programmes I saw within a week recently.
In the dramatisation of The Name of the Rose currently being shown on the BBC, John Turturro, an American actor, said “an ‘erb”. He was actually playing an Englishman, albeit one in the middle ages, and he has adopted an English accent throughout.
On an episode of Supergirl, David Harewood, a British actor, said “a herb”. Now, his character is supposed to be a Martian, but one that has been on Earth for a long time and he speaks with an American accent.
Both pronunciations sounded wrong in context.
I was once told that ‘an’ before an h-word should be used when the accent of the word is on the second vowel – hence ‘an hoTEL’ and an ‘hisTORical house’ but not ‘an HISTory’.I think it’s not so much a rule as a convention.
This is interesting. That second syllable rule would fit with the French version, but as soon as you replace ‘an’ with ‘a’, the stress then goes onto the first syllable, probably because of the need to stress the ‘h’.
I once read that when a Member of Parliament informed a colleague that he had ‘an ‘orrible ‘eadache’, the response was that he needed a couple of aspirates.
Note that Fowler says “now that the h in such words is pronounced” – clearly implying that in the past it was not. As commenters above have noted, that shift toward pronouncing those initial /h/ sounds is not universal, and speakers from the London area tend to elide them.
I always say “an hotel” without pronouncing the h but I feel old-fashioned when I do so. Not pronouncing the l in “golf” is probably more unusual these days. I am sixty years old and live in the English West Midlands.