The Morris dance...
...is traditionally danced on May 1, to welcome in the summer. Its history is a bit confused, possibly because it's often danced near pubs, but it is now the English folk dance. The dancers usually wear white, and have bells sewn on their clothes. It is danced by both men and women, and is certainly now danced in the United States, too.
I know this because I saw the Dark Morris danced in a bookshop in Chicago some years ago.
I'd invented the Dark Morris for another book called Reaper Man (at least I think I invented it), and a Morris team (officially known as a side) turned up in all black, just for me. They danced it in perfect silence and perfect time, without the music and bells of the "summer" dance.
It was beautifully done. But it was also a bit creepy. So it might not be a good idea to try it at home...