In the 1700s, a gentleman’s white wig not only told other gentlemen that he was a gentleman, it could also signify what kind of gentleman he was. There were general styles worn by businessmen and planters, but there were also particular styles linked to professions.
Doctors, for example, wore a “physick’s wig,” which Karin Calvert says “had a woolly, teased appearance known as a natty bob.” In 1775 the British magazine Connoisseur said, “a physician would seem ridiculous prescribing in a bag-wig,” a type with a queue or ponytail at the rear in a cloth bag worn by laymen. Examples can be seen in portraits of Dr. John Lanzalotti and Dr. John Ash, and this satirical print from 1784. John S. Copley’s portrait of Dr. Silvester Gardiner seems to show a neater variation, perhaps reflecting his retirement from active medicine.
Another specialized subset was the “parson’s wig,” suitable for ministers and characterized by its “rows of neat curls.” An early-1700s version appears in this portrait of the Rev. Dr. Cotton Mather by Peter Pelham, the best engraver to work in Boston in that century (and, for a short time, J. S. Copley’s stepfather). Boston's ministers in the pre-Revolutionary period wore variations on this style: Rev. Dr. Jonathan Mayhew; Rev. Dr. Charles Chauncy; Rev. Dr. Mather Byles, Sr.; and Rev. Dr. Ezra Stiles.
During the Revolution, a French visitor to Boston said of the Rev. Dr. Samuel Cooper:
He writes sprightly verses, and carries certainly much cleverness under the immense wig of a clergyman, which he wears bigger and more heavily powdered than any of his brethren.The same style was used by men in another learned profession, the schoolmaster. A former student at Master John Tileston’s Writing School recalled that he “wore his wig, however, to the last, and never appeared at school without it. The pattern was the same that clergymen wore, and the engravings of Dr. [George] Whitefield and Dr. Samuel Cooper, will give an exact idea of it.”
The legal profession is the only one in which people still wear eighteenth-century-style white wigs, at least in many parts of the British Commonwealth. Different shapes distinguished judges, barristers, and solicitors. (In Massachusetts, the lawyers grouped by the Boston bar as “barristers” and “solicitors” did the same legal tasks; the first group were simply more senior.) Copley painted Samuel Quincy, the province’s Solicitor General and thus a leading attorney, in a barrister’s wig. The less skilled (and therefore less expensive) artist Benjamin Blyth produced the first portrait of John Adams in similar headgear.
Of course, a gentleman could choose whatever style within particular groupings he thought would best fit his face, fashion sense, and budget. And some men, such as Boston's Dr. Joseph Warren and George Washington, wore their own hair with a dusting of white powder.
(There were also specific types of wigs for footmen, coachmen, and other servants, but those demonstrated the genteel taste and wealth of the wearers’ employers, not the wearers themselves.)
I have to admit my eye for the differences among groups of wigs isn’t well developed. It feels like when I was a boy and my best friends could identify different makes of car from blocks away, but I hadn’t learned the distinctions. ("That's a, um, blue car?") In the eighteenth century men could probably spot and grasp the difference between a wig with two side-curls versus one with three the same way my mom knew the difference between a three-hole Buick and a four-hole Buick.