Instruments with double course strings have existed since the time when the lute was used in renaissance and baroque music. The first early guitars generally were strung in double course as well. That is the way things change, step by step. The first guitars with single strings appeared in about 1785, more on this in another article.
Many double course guitars ( when of good quality) were "beheaded" and changed into 6 strings.(pic.1 french guitar) ,Around 1880-90 immigrants from South America (pic mexican bacho-sexto) and Europe started to bring double stringed instruments to the USA.(pic.2, instrument from the Azores).In Italy of course many multi- stringed instruments were built, such as mandolins (pic3mandolin )and guitars.
One of the earliest I have found is this 11-string guitar(pics) , probably made by Lyon and Healey. A catalogue of this company from 1905 mentions 11 and 12- string models .( for more information on the history of the 12-string guitar have a look at this excellent article )
Also this very rare example (possibly the only one made), by the Washburn company, went through my hands, courtesy of Dutch collector Jurgen Terijdt.) (pics)
Next is an example of the famous 12 string played by great early bluessingers such as Blind Willy Mctell and Leadbelly .
They were made in different sizes and this one is a smaller bodied one. (pics)
Then there came a period when the 12 string was heard less, and it wasn't till the 60's when it was revived by people in the folk scene such as Pete Seeger. Around this time companies like Gibson started making 12 strings in bigger numbers again ) models like this B-25, with their wide necks) (pic).
Players in England also started looking for the 12 ,and here are some pictures of a guitar specially made for made by John Bailey for Bert Jansch, a former member of Pentangle.(pics), It features brazilian rosewood back and sides and swiss spruce top. It was allegedly played by Jimi Hendrix during some London BBC sessions.
Other companies who have made good 12-strings consistently are Martin and Guild.(pics)
Electric 12 strings were built by Rickenbacher ,with their inventive headstock,housing the machineheads in offset fashion, used by George Harrison and Roger McGuin(pic)
More rare is this Framus 9-string, with the 3 top strings doubled. Only 50 of these were made!(pic). Dutch indo-rock guitarist Andy Thielman did use a Fender with extra machineheads added to get that sound, to keep his secret he used to tie a bandana around the headstock! (pic)
The last picture is of a custom built 12-string by Don Musser, who builds only a few guitars every year ,made with the finest spruce, rosewood and koa, this is an exceptionally light playing 12 string.(pics)