Fast food has its staples: hamburgers and cheeseburgers, french fries, soda, probably a chicken option such as nuggets or a grilled sandwich. More "exotic" items include onion rings, milkshakes, hash browns, and fried fish items. But rarely—Wienerschnitzel franchises excepted—are hot dogs on the menu. For McDonald's, there's a reason. Blame Ray Kroc, the man who bought the tiny company in 1954 and turned it into a multi-billion dollar fast food behemoth.
In 1977, Kroc wrote an autobiography titled Grinding It Out: The Making of McDonald's, documenting his vision for burgers and fries made quickly, cheaply, and at immense scale. In the book, he notes that McDonald's is always experimenting with new potential additions to the menu, going so far as to explicitly state that "it's entirely possible that one day we'll have pizza [on the menu]." (Pizza was indeed tested, and made the menu of roughly 500 stores before being withdrawn. Per Wikipedia, though, McPizza is still available at three McDonald's locations, one each in Spencer, WV; Orlando, FL; and New Haven, CT.) But Kroc singled out hot dogs as the one food beyond the even the pale of experimentation: "On the other hand, there's damned good reason we should never have hot dogs. There's no telling what's inside a hot dog's skin, and our standard of quality just wouldn't permit that kind of item."
Nevertheless, Kroc's edict did not withstand the test of time.
McDonald's has tested hot dogs—the McHotDog, naturally (shown above)—in a number of markets, most notably at the location in Toronto's SkyDome (now the Rogers Centre), home of the Toronto Blue Jays. Apparently, in Canada, there's nothing more American than a hot dog at a baseball game.
BONUS FACT: New York City is rife with carts (such as the one seen here) selling hot dogs, pretzels, cold drinks, etc., with the core products running a buck or two, depending on location. Central Park spots can run as high as $175,000 annually, and in 2008, one vendor bid over $600,000 for the exclusive right to sell wieners outside the Metropolitan Museum of Art.