The maritime history, the literary air, the Federal-style old New England homes: The plentiful allure of the two major islands off the southern coast of Cape Cod is readily apparent all summer long. When the weather is warm, the respective populations of Nantucket and Martha's Vineyard balloon with the hoi polloi. The Clintons and Obamas have done the Vineyard; Jack Welch and Bill Belichick do Nantucket.

In fact, almost everyone who visits the islands is stubbornly partial to one or the other. Broadly speaking, Nantucketers like to keep their island quaint and tidy, with its cobblestone main drag and its preppy uniform of salmon-colored chinos – "Nantucket reds." Vineyarders, on the other hand, tend to be a scruffier lot – plenty of bait-and-tackle-shop regulars in bushy facial hair and Black Dog sweatshirts.

From a global perspective, these tiny destinations are almost literally two peas in a pod, but on the local level, their relationship has never been cozy. That animosity is borne out every November, not long after the "wash-ashores" have pushed off and the hardy year-rounders have hunkered down, in one of the country's most spirited and idiosyncratic high school football rivalries.

Both teams have a history of overachievement despite small school populations, each making routine appearances in Massachusetts divisional Super Bowl championship games. And for decades, the purple-clad Vineyarders and the navy blue Whalers of Nantucket have kicked off the traditional end-of-season Thanksgiving rivalry games with an inter-island classic – the Island Cup – on the weekend before the holiday.

It's a great time to visit the islands (the games alternate each year; this season's is November 22nd on the Vineyard). Rates are comparatively reasonable – rooms at Vineyard Haven's Mansion House, for instance, start at $179, as opposed to $279 in-season. And businesses have not quite boarded up for the winter; in November on Nantucket, they're just preparing for the annual Christmas Stroll, a tourist attraction that's straight out of Currier and Ives.

Two years ago the Island Cup game was added to the Great American Rivalry Series, sponsored by the U.S. Marine Corps. Given the ferocity of emotion on both sides of the ball and the field – two years ago we watched a reckless young Nantucket booster race in front of the Vineyard's home fans waving a Jolly Roger flag, only to be blindsided by an infuriated counterpart who sprinted down from the grandstand – it's not a bad idea to have a military presence on hand.