Many, like Ruiz Hot-Dogs on Sixth Avenue, work step-side carts with two-item menus of Sonoran hot dogs and soft drinks. Set in dirt and gravel parking lots, beneath makeshift shelters, under mesquite tree arbors, these peripatetic vendors serve fast food for day laborers, craftsmen and policemen, the typical patrons of traditional hot dog stands in any town.

Other champions of the Sonoran style, like El Güero Canelo, with two Tucson outlets, have evolved from carts into full-scale restaurants. (At the Twelfth Avenue location, two of the three spaces where burritos, tacos and hot dogs are cooked and assembled remain on wheels, but the prospect of mobility is now far-fetched.)

Image THE SONORAN WAY Ruiz Hot-Dogs in Tucson is fine by Luis Galindo. Credit... Chris Hinkle for The New York Times

One Sunday afternoon, as a mariachi band played, an after-church crowd, half Anglo and half Hispanic, thronged El Güero’s outdoor dining pavilion. Babies cried. Teenagers table-hopped. And parents argued that, rather than order a second hot dog, children should fill up at the salsa bar at the back of the pavilion, stocked with peeled cucumbers, sliced radishes and chunky guacamole. Front and center on every third table was a Sonoran hot dog.

For at least the last 40 years, likely longer, borderland vendors, in Tucson and elsewhere, have been refashioning the hot dog with a cloak of bacon, a clump of beans and a chop of tomatoes and onions, followed by squirts of mayonnaise, mustard and salsa verde. (Ketchup and other condiments show up, too. More recently, some vendors have begun offering a topping of crumbled potato chips.)