Photo: Prayitno / Thank you for (12 millions +) view from Los Angeles, USA / Wikimedia Commons · CC BY 2.0
Much of San Francisco sourdough's tang comes from a bacterium, not a yeast: Lactobacillus sanfranciscensis, identified in the city's sourdough in the 1970s and named after it.
A round loaf of tangy sourdough is hollowed out and filled with hot, creamy clam chowder, eaten by scooping out the bread as you go until the bowl itself is gone. Walk-up stands along Fisherman's Wharf hand it over in a paper wrap for eating on the pier.
Why it's made this way: San Francisco's Gold Rush-era bakeries developed the city's signature sour, wild-yeast sourdough, and Fisherman's Wharf vendors turned the loaf itself into edible tableware for the local catch.