Ko’olau Guitar & ‘Ukulele Company was started as a small family business in 1979, as Kitakis Stringed Instruments on Oahu. They have since expanded considerably and now work out of a factory in Wahiawa. To begin with they did mostly repairs but they did make some new instruments, including Mandolins. Now though they specialise in making new Ukuleles and Guitars and when people talk about the "Big K's" in Hawaii this is one of them. 

Ko'olau does all scale from Soprano to Baritone plus Lili'u and Taropatches as standard ranges and has a full custom shop with one of the specialities being inlaid fretboards. Unusually for Hawaii though they have a far greater selection of woods used for their standard ranges and they have also added some more contemporary models like solid electric ones and archtops. As time goes on they say they are increasingly cutting down on the standard models and concentrating on the custom ones. 

Pono

The instruments branded Ko'olau are all made in Hawaii but the company also has a factory in Java, Indonesia that produces their less premium line, Pono, (though I believe that early production came from China, certainly it is the case that some Pono Ukuleles have been made in China). This line also has a full range of scales and string numbers, even solid electrics, in a number of woods, but there is no custom shop. 

As well as the Ukuleles and Guitars they do market the Ko'olau Gold Ukulele strings which are very widely available and a distinctive yellow gold colour, (though they do make other types of string too)