We are a nation united by our love of processed meat between a bun. At least that’s what I believed before a friend and I tore through the half-dozen different hot dogs on the menu at Shaggy’s, a Mid-City restaurant painted mustard yellow and ketchup red. I lost my innocence and learned that we’re a nation as divided by dogs as we are by pizza preferences and allegiances to the many styles of barbecue beef and pork.

The Chicago dog opened my eyes to our division. Of the many toppings on th...