Ah, the tartan! What a glorious tradition, each clan to its own tartan! Imagine them running over Culloden Field in their Highland Charge, displaying to the enemy which families were arrayed against them! How tragic it was when the plaids were banned for most of the rest of the 18th century!
Except not. Time for some sartorial (i.e., clothing) mythbusting!
Here is a portrait of John Campbell, from 1749:
We have a problem here. The Campbell plaid, as we know it, is predominantly blue, green, and white, and looks like this.
So he is definitely not wearing Campbell plaid. (In fact, he's wearing two plaids that aren't "Campbell plaid" – your eyes may be watering too hard from that outfit to tell, but those tartans are different top and bottom). Why not?
Campbell plaids did not exist in the 18th century. Neither did Stewart plaids, or MacDonald plaids, or MacIntosh plaids, or any other form of official standardized clan plaids. There were very likely regional variations caused by the availabilities of dyes and local weaving techniques, but the official tartans as we know them are a product of the early 19th century, specifically of a firm called Wilson's of Bannockburn.
At that time, Scotland was hot. Highland regiments won renown for their fighting against Napoleon. Sir Walter Scott's 1814 book Waverley romanticized the '45 uprising like dang and whoa. King George IV even came to Scotland in 1822, and wore tartan! Wilson's knew a good trend when they saw it, and began weaving like crazy on those newfangled industrial looms. This, by the way, is another nail in the coffin for the "plaids as traditional Highland attire" argument – the plaids we see today are completely beyond the capacity of a Highland homespinner, both in weaving and dyeing. (Want to try some virtual weaving yourself? See links below!)
Soon, Wilson's's ('s's's's) tartans were flying off the shelves. To keep track of all the patterns, or perhaps to simply merchandise them better, the tartans were given clan names. The final capping touch on this was the forgery of the Vestiarium Scoticum (a book, and not a skin condition, although it sounds like one) by John Sobieski Stuart and Charles Edward Stuart, two brothers who claimed to be the descendents of Bonnie Prince Charlie. The book, which they said came from an old manuscript, claimed to lay out pre-Culloden tartans by clan. As fake royals trying to bond with the local population and score some freebies like room and board, the Sobieski Stuarts probably claimed this faux sartorial (word of the day!) expertise to shore up their Scottish street cred.
Need more evidence? Look at the 1746 David Morier painting of Culloden, in which the Scots clearly are not wearing organized plaids. The tartans shown also do not align to the 19th century plaids assigned to the clans we know were at the battle. (There are also some more amazingly eyewatering tartan-on-tartan outfits here – I'm surprised the Hanoverian side could see to aim their muskets.) Eyewitness accounts of the battle support the painting as well. The Jacobites were distinguished by white bonnets, or the berets with white bows shown in the painting. After the battle was lost, the vanquished frequently ditched the bonnet to pass for Royalists. Clearly, this would not have worked if the other 8/10ths of your outfit screamed "Member of a Jacobite Clan."
Some people don't deal well with this revelation. My professor recounted giving a presentation on the above portrait of Campbell and receiving a question from a man who wanted to point out to her that it couldn't be John Campbell, since it wasn't a Campbell plaid. She explained what I've just gone over here – that the "Campbell plaid" is 19th century construction, etc., etc., and he nodded and nodded, and when she finished, he said, "I understand what you're saying, Professor, but that's not a Campbell plaid." The tourist industry also is very fond of the tartan system, as it enables them to sell mass quantities to Scottish diaspora tourists seeking a bit of heritage to take back. (Which is completely fine with me - the tartan can still connect you to Scottish heritage, or to other wearers, or can just look fun, regardless of what year it was designed. I like tartan. I just want to point out its real history.)
Nowadays, tartans are policed very seriously by the Scottish Register of Tartans, which you can think of as a patent bureau for tartan patterns. If you made a tartan using Tartan Maker or Tartan Designer or Interactive Weaver (go on, it's a hoot) or another progam, I'm sorry to say you can't just declare it your tartan and start making kilts. You must submit it (and pay a fee), and have your submission approved as different enough from all existing tartans to justify its own registration. With everyone from Alberta to Zambia getting in on the act, you can imagine things get tighter every year.
By "policed," though, I don't mean that people will come and tear a tartan off you if they don't you deserve it. Mostly it relates to manufacture and naming rights. People "in the know" would frown on wearing the royal family's three Balmoral tartans if you're not actually a royal (they won't even manufacture them for you in the UK), but tartan-wearing is basically self-policing. If you want to wear one just because you like it, I don't think people would mind. Just don't lie and say you're their long-lost cousin
Coming up next time: the "banning" of the Tartans, and what is a plaid?