San Francisco sourdough: history, science and where to buy it

San Francisco sourdough is a tangy, chewy, crusty bread made with a natural starter instead of commercial yeast, and the city has been baking it since the Gold Rush. Its sour flavor comes from wild yeast and lactic acid bacteria living in the starter, including one species named after the city itself. Here is where it came from, what makes it different, and how to find a good loaf.

Why is San Francisco famous for sourdough?

The story begins with the Gold Rush. Gold was found in California in 1848, and by 1849 San Francisco's population had jumped from around a thousand people to tens of thousands. Miners and settlers baked with sourdough starters because they did not depend on store-bought yeast; a starter could be kept alive and fed indefinitely. Prospectors leaned on it so heavily that "sourdough" became a nickname for the miners themselves.

In 1849, a baker from a French baking family began making bread in San Francisco with a starter bought from the miners. His loaves came out with a distinct sour tang, and the bakery he founded is still baking. It describes its starter, the "mother dough," as having been kept going since 1849.

What makes San Francisco sourdough taste different?

Sourdough starters are communities of wild yeast and lactic acid bacteria. The yeast makes the dough rise; the bacteria produce acids that give the bread its sour flavor and help it keep.

Food scientists studying San Francisco starters identified a previously unknown bacterium responsible for much of the characteristic tang. They named it after the city: Lactobacillus sanfranciscensis. The bacteria turned out not to be unique to San Francisco; bakers find them in starters around the world. Still, the name stuck, along with the city's claim on the style.

Long fermentation, a hot oven and a well-developed crust do the rest. A classic San Francisco loaf has a dark, crackly crust, an open and chewy crumb, and a sourness that is noticeable but should not overwhelm.

How do you pick a good sourdough loaf?

Look and listen before you buy.

• The crust should be deeply browned, even dark in places, and crackle when pressed. A pale crust usually means a shorter bake and less flavor.
• The crumb should be glossy and open, with irregular holes.
• The smell should be tangy and wheaty, not yeasty.
• The weight should feel substantial for the size.
• The label matters. Real sourdough uses a natural starter. Some supermarket breads add vinegar or commercial yeast for a quicker "sour" flavor; read the ingredients if you are buying packaged bread.

Bakeries usually sell their loaves through the day, and the best-known bakeries can sell out by afternoon. Go early, or ask what time the loaves come out of the oven.

Where can you eat sourdough in San Francisco?

Sourdough is everywhere in the city, from sandwich shops to fine dining tables, but a few experiences are classic.

The bread bowl at Fisherman's Wharf. Clam chowder in a hollowed sourdough round is the city's best-known tourist meal. A flagship bakery on Jefferson Street at Fisherman's Wharf has a railing over its showcase kitchen where you can watch the loaves being shaped and baked.

Neighborhood bakeries. A newer generation of San Francisco bakeries made long-fermented country loaves famous far beyond the city. Many neighborhoods, including the Mission, the Richmond, the Sunset and Hayes Valley, have a bakery with a line on weekend mornings.

Farmers markets. Bakers sell at the city's farmers markets, including the market at the Ferry Building, which is a good place to taste several styles in one trip.

Is sourdough healthier than other bread?

Many people find long-fermented sourdough easier to digest than some quick commercial breads, and the fermentation changes the bread's texture and flavor. It is still bread made from wheat, so it is not gluten-free and is not suitable for people with celiac disease. If digestion or nutrition matters to you, talk to a doctor or dietitian rather than relying on bakery claims.

How do you keep sourdough fresh?

Sourdough keeps better than most bread because of its acidity.

• Store it cut side down on a board, or in a paper or cloth bag, for the first day or two.
• Avoid the refrigerator, which makes bread go stale faster.
• For longer storage, slice it and freeze it, then toast slices straight from the freezer.
• A day-old loaf revives well in a hot oven for a few minutes.

Can you take sourdough home on a plane?

Bread is generally fine to carry on domestic flights, and a whole loaf travels well in a paper bag inside your carry-on. Airport security and customs rules differ by country, so check the rules for international trips, particularly if you are bringing bread or a starter abroad.

How do you find the loaf you liked again?

After a few days of bakery visits, the loaves start to blur together. On Mosey you can rate the bakeries you visited and the specific loaves and pastries you bought, with photos, keep a list of bakeries to try next, and follow friends to see which ones they rate.

More guides to read next:

• San Francisco Chinatown and dim sum: a food guide
• Cioppino and Dungeness crab season in San Francisco
• Ferry Building and farmers market in San Francisco: a visitor guide

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