The Possessive Apostrophe.

Sensitive subject. I learned today that there are only five place names in the whole of America that take possessive apostrophes (as in Martha’s Vineyard.)

If English greengrocers had their way, there’d be a sixth:

Niagara Fall’s.

English greengrocers are legendary for their (often, I suspect, mischievous) misuse of the possessive apostrophe. It's all about working class rebellion.