Chicago did not invent pizza, but it rebuilt it from the crust up. In 1943, Ike Sewell and Ric Riccardo opened Pizzeria Uno on the corner of Ohio and Wabash, serving a tomato pie with the architecture reversed — cheese on the bottom, sauce on top, and a thick, buttery crust that climbed the sides of a blackened steel pan. The deep-dish was born not as tradition but as defiance, a deliberate break from the Neapolitan flatbread that had crossed the Atlantic with Italian immigrants. Within a decade, competitors emerged across the Near North Side, each claiming the original recipe and each tweaking the formula: cornmeal in the dough, sausage beneath the cheese, a second crust for the stuffed variation that arrived in the 1970s. Today, Chicago's pizza landscape spans four distinct styles, each rooted in a different decade and neighborhood. Deep-dish remains the most famous, but tavern-style — thin, square-cut, and cracker-crisp — dominates the South Side and predates Uno by years. Stuffed pizza, with its double crust and molten center, emerged as a 1970s maximalist answer to the deep-dish. Pan pizza, baked in rectangular trays and sold by the slice, traces its lineage to Sicilian sfincione and thrives in corner bakeries from Bridgeport to Little Italy. A Chicago pizza walking tour connects these threads, moving between wood-paneled dining rooms, corner taverns, and third-generation ovens, each stop a living argument in the city's longest-running culinary debate. The tours depart daily, beginning mid-morning when the ovens are already firing and the dough has proofed overnight. Groups walk two to three miles, stopping at four pizzerias chosen not for tourism but for their role in the city's pizza genealogy. Guides narrate the immigrant waves, the labor strikes, the rival recipes, and the newspaper columns that turned pizza into civic identity. Tastings are served family-style, portions sized for comparison rather than a full meal. The route shifts by season and operator, but the structure holds: tavern-style first, deep-dish second, stuffed or pan to close, with a final stop at a decades-old bakery or cheese supplier. The walk is urban, concrete, and unapologetically specific — no riverwalk detours, no architecture tangents, just the blocks where Chicago pizza was forged and the ovens that still bake it the old way.