I've been impressed by the quality of research done on this forum. I have "drunk driver" meaning one who drives an automobile while intoxicated from 1948. I'm pretty sure it's older than that. Can anyone find an earliest attested date of that phrase in that sense, with evidence showing it in a reproduction (i.e. digital scan, not transcription) of a dated publication? And would there be an objection if I drop such queries here from time to time?
The crime (or misdemeanor) of drunk driving—and use of the term drunk driver to characterize an offender guilty of it—evidently goes back in some municipalities to the days of the horsed carriage. From "Police Courts: Friday, July 22: Perth," in the [Perth, Western Australia] Inquirer and Commercial News (July 29, 1898):
A Drunk Driver.—Charles Hillman was charged with having been drunk while in charge of a horse and cart in Hay-street. The accused, it was stated, was sent out in the morning by his employer, Mr, Gullen, to deliver a round with a baker's cart. He, however, got hopelessly intoxicated, and neglected his master's property and business. The accused was sentenced to 21 days' hard labor.
Application of the term drunk driver to the impaired driver of a horseless carriage appears at least as early as 1921. From "Notes and Comments," in the [Barcaldine, Queensland] Western Champion (January 1, 1921):
There is one magistrate in England at least who thinks some of the laws require revising and bringing up to date. For instance he considered he should have greater power for dealing with drivers of motor cars who have indulged too much in the cup that cheers, but also inebriates. While dealing with a case the other day he complained that "It is ridiculous that I can only fine the drunk driver of a deadly thing like a motor car the same as a drunk driver of a donkey cart."
To see the original articles from which these excerpts came, simply click the linked article names.
As Hot Licks notes in a separate answer, the phrase drunk[en] driver goes back considerably farther than the late 1890s. The earliest instance I found in a Google Books search is from a letter to the editor written by G. Cumberland of Bristol, England, dated October 18, 1814 touching on the regulation of stage-coaches, printed in The Monthly Magazine (April 1, 1815):
As to the expenditure of constitution, that or the risk of a broken neck is not to be expected to be thought of, by a being, who imagines he exalts himself in the world's opinion, by suffering a drunken driver to extort money from him at every stage, under penalty of being insulted with foul language, (yet knows the fellow is amply remunerated for his services by the coach-owner;) and as often repels the travelling vagrant on foot with that harshness and unfeeling pride, that brings the blush of indignation from the wounded heart.
This is the same instance that Hot Licks identifies as "Drunken driver from 1815."
The instance of "Drunk driver from 1848" in Hot Licks's answer is actually from an entry in Walter Scott's diary, dated May 28, 1828, reprinted in J.G. Lockhart, Memoirs of the Life of Sir Walter Scott, Bart., volume 9 (1848):
Our elegant researches carried us out of the highroad and through a labyrinth of intricate lanes, which seem made on purpose to afford strangers the full benefit of a dark night and a drunk driver, in order to visit Gill's Hill, in Hertfordshire, famous for the murder of Mr. Weare.
The earliest instance that a search of the British Newspaper Archive turns up is this one, from "The Fleets," in the Hull [Yorkshire] Packet (May 21, 1805) [combined snippets]:
On Saturday night, the Leeds True Briton coach, was overturned coming from Leicester, through the carelessness of a drunken driver, who turned it out of the road where no impediment existed to interrupt his progress. There were five inside passengers and several outside, all [?] of whom were much hurt.
These three instances, of course, involve drivers of horse-drawn conveyances.
The earliest example the OED has of drunk-driver is from 1948. They do however have a US example of drunk-driving from 1937. 937 Literary Digest 30 Oct. 8/1 In view of the rise in accidents from this cause, we will concentrate on just one thing—drunk driving.
The phrase 'drunken driver' appears at least as early as 1770, in Gentleman's Magazine, v 40, where it is used in an adaptation (called a "translation") of Calderon de la Barca's play, El Escondido y la Tapada:
...the coach appeared to be Guzman's the father of Marcella, which had been overturned by a drunken driver....
On 04 Dec 1894, 'drunk driver' appears with reference to a railway engineer in the Aberdeen Journal (Aberdeen, Aberdeen, Scotland; paywalled, emphasis mine):
THE DRUNK DRIVER AND HIS ENGINE
... An engine-driver, who was intoxicated, became possessed of some delusion, and in this condition started with his engine and a post van at full speed in pursuit of a passenger train....
'Drunk driver' with reference to motor vehicle operators could have occurred as early as 1769 (first steam-powered automobile), but does not seem to have appeared in print before 1912. Then, in the 19 Dec Silver Lake Mirror (Silver Lake, Kansas; paywalled, emphasis mine), it appears in an article reprinted from the Leavenworth Times. The context is informative:
Danger from Drinking Men
The Pennsylvania Railroad Company...took measures recently to ascertain which of its thousands of employees are in the habit of using intoxicating liquors and they have seen to it that all such men are taken from places in which they may endanger the safety of trains...The great railroad does not trust a man who drinks.
Some years ago the great Santa Fe system began to discourage drinking by refusing to employ men who were moderate drinkers. The officials realized that what the man calls a moderate amount of stimulant may so affect his brain that he is no longer to be trusted.
A great eastern paper, in a recent issue makes a bitter complaint of the automobile because it is used by men who muddle their brains with drink and then become unsafe as drivers...When [a] drunk driver comes along better take to the fence corner and pray that he doesn't find you.
(Hint: If you're going to be doing much of this stuff you need to learn how to use Google Ngram. It is a very powerful tool if you take some time to learn its quirks.)