It all started with a Dutchman who "advertised for 15 ginger models to paint - only to be deluged with e-mail responses. The 15 turned into 150, whom he photographed. But when many of those who didn't get selected voiced their disappointment, Mr Rouwenhorst decided to make an annual event of the redhead gathering."
Reading some of the quotes about how hard it was growing up with ginger hair is a little odd (why are they singled out). Red hair seems to occur all over but the biggest density now is in north-western Europe (with a lot in England, Scotland and Ireland). Historically it was found in China too.
It's the rarest natural hair colour in humans. To quote from Wikipedia:
Studies by Bodmer and Cavalli-Sforza (1976) hypothesized that lighter skin pigmentation prevents rickets in colder latitudes by encouraging higher levels of Vitamin D production and also allows the individual to retain heat better than someone with darker skin. Rees (2004) suggested that the vividness and rarity of red hair may lead to its becoming desirable in a partner and therefore it could become more common through sexual selection.
Harding et al. (2000) proposed that red hair was not the result of positive selection but rather occurs due to a lack of negative selection. In Africa, for example, red hair is selected against because high levels of sun would be harmful to fair skin. However, in Northern Europe this does not happen, so redheads come about through genetic drift.
Aside from well-known famous red-heads, such as Queen Elizabeth, in Greek mythology Menelaus (husband of Helen [of Troy] and king of Sparta) and Achilles were supposed to be red-heads, so was King David and the Prophet Muhammad used to dye his hair red with henna.