Updated September 2026

September is Sourdough September. April 1st is National Sourdough Bread Day: two occasions to focus on the world’s oldest leavened bread.

For those who really celebrate their daily bread (we’re among them), there’s Real Bread Week, usually beginning the the last Saturday to the last Sunday in February‡. This annual international campaign, begun in the U.K., is dedicated to promoting additive-free bread and honoring the artisan bakers, millers, and teachers who create it.

Known for its crisp crust, chewy interior, and tang, sourdough is the oldest form of leavened bread.

Born in ancient Egypt, its history spans 6,000 years and multiple continents.

Popularized in the U.S. during the San Francisco Gold Rush, it was reborn in the modern artisan bread movement of the 1980s, and got a lift during the pandemic when people stuck at home took up bread-making.

Below:

> What is sourdough?

> The history of sourdough.

> Sourdough comes to America.

> Sourdough today.

> The history of bread, before and after sourdough.

> Sourdough names in 19 other countries.

Elsewhere on The Nibble:

> The year’s 20+ bread holidays.

> The different types of bread: a photo glossary.
 
 
1. WHY SOURDOUGH DIFFERS FROM OTHER WHEAT BREAD

Sourdough describes the leavening method: bread rises with a fermented culture of wild yeast and lactic-acid bacteria, usually called a starter or levain, rather than relying solely on commercial baker’s yeast.

The dough is created during a long fermentation, originally using naturally occurring lactobacilli bacteria and wild yeasts (other types of breads use cultivated yeasts, which became available only in the 19th century).

In comparison with breads made with cultivated yeast, sourdough usually has a mildly sour taste and aroma, the result of the lactic acid produced by the lactobacilli.
 
 
The Sourdough Starter

The preparation of sourdough begins with pre-fermenting, using a “starter” made from flour and water (photo #3).

The starter is also known as levain, the chief, chef, or head. Since the ratio of water to flour varies by baker, it can be a fluid batter or a stiff dough.

The starter helps to develop the uniquely tart flavor of sourdough bread.

Starters are maintained for years, even generations. The colony of bacteria and yeast inside the dough is kept alive by the baker, who needs only a piece of it to bake a new batch of bread.

If you bake bread in a bread machine, you’ve probably noted that sourdough typically doesn’t work in one. The rise time of most sourdough starters is longer than that of breads made with baker’s yeasts. Sourdough requires conventional baking techniques.

> Here’s how to make your own sourdough starter, from King Arthur Baking.
 
 
2. THE HISTORY OF SOURDOUGH

How Sourdough Leavening Began

In antiquity, bread was an essential staple. Workers were paid partly in bread and beer.

Bread production has relied on the use of sourdough as a leavening agent for millennia.

Before the Egyptians corralled wild yeast to leaven bread, the only option was flatbread—chapati, dosa, inerja, lavasch, matzoh, naan, pita, tortilla, and others.

The development and use of [cultivated] baker’s yeast as a leavening agent dates back only to the mid- to late-19th century.

Thus, for the millennia before the introduction of commercial yeast, bakers relied on wild yeasts and lactic acid bacteria—naturally present in flour and the environment—to get bread to rise.

The discovery of leavened bread was likely an accidental by-product of brewing and porridge-making in the ancient Near East. It’s most prominently documented in Ancient Egypt.

(One of the oldest Neolithic sourdough breads/porridges was found in a Swiss excavation site near Twann, Switzerland, dating to c. 3700 B.C.E.)

The ancient Egyptians were leaders in bread baking, and archaeologists believe sourdough bread originated in Egypt, c. 4000 to 3500 B.C.E.

Each village had a communal oven*, a central feature of village life from antiquity through the 19th and early 20th centuries.

How did the happy accident that created sourdough occur?

• When raw grain flour and water sit at ambient temperatures, the airborne wild yeasts (Saccharomyces species) and lactic-acid bacteria (Lactobacillus species) naturally present on grain husks begin to ferment the starches and sugars.
• Fermentation produces carbon dioxide gas bubbles. When trapped in a dough made with gluten-containing grains (like emmer, spelt, or early wheat varieties), the trapped gas causes the dough to puff up and rise rather than remain dense.
• Bakers discovered that saving a small piece of this bubbling, fermented dough (called a “mother” or starter) to mix into the next day’s batch produced lighter, airier, and more flavorful loaves reliably.

Otherwise, they used barm†, the frothy foam that rises to the top of fermenting beer or ale. It was skimmed and used as a natural leavening agent.

The process spread along trade routes through the Middle East and into what is now Europe.

Ancient Greeks, c. 500 B.C.E., turned bread baking into an art, experimenting with different grains.

They invented the front-loaded bread oven and a wide variety of doughs, loaf shapes, and styles of bread to pair with specific foods.

Baking became a profession, and people began to buy their bread from skilled bakers.

The Romans, c. 100 B.C.E. to 400 C.E., expanded on Greek techniques and improved milling technology. They invented the concept of grinding grain by rubbing it between two stones.

Even after manual grinding was replaced by revolving grindstones driven by beasts of burden or slaves, grinding was a time-consuming process, and leavened bread was a costly food.

White bread, also invented by the Romans and made by sifting the grains through linen, was even costlier.

Ironically, given what we know about nutrition today, the poor ate dark, whole-grain bread, and the wealthy ate white bread, stripped of essential nutrients.

This class separation by bread continued until the Industrial Revolution made the more elegant white bread available to everyone.

Continental Europe. Bread was the cornerstone of the European diet, often providing more than half of daily calories. Sourdough was the common bread.

In the Middle Ages, 500–1500 C.E., sourdough remained the standard leavening method in Europe. Rye sourdough was especially important in Northern and Eastern Europe, where wheat was less available.

Bakers used sourdough starter from a prior batch to create the new batch.

Sourdough remained the usual form of leavening in Europe into the Middle Ages. Sourdough starters were passed down for generations (and still are).

Then, it was replaced by barm, the yeast-laden foam that forms in the process of brewing alcohol (for bread, the barm typically came from beer brewing).

It took a few more centuries for scientists to learn to culture yeast, so bakers no longer had to rely on barm or sourdough starter.

By the Renaissance, the 1500s–1700s, bakers across Europe had developed regional sourdoughs. French pain de campagne and German rye sourdoughs became staples.

During the Industrial Revolution, 1760 to 1840, scientists isolated Saccharomyces cerevisiae, brewer’s yeast.

Commercial yeast became widely available following the introduction of Fleischmann’s Yeast (introduced in 1868, patented and commercialized in 1876), enabling faster, more predictable rising than obtained with sourdough.

As a result, sourdough began to decline in much of Europe and the U.S., and in the early 1900s, industrial bread—using commercial yeast, additives, and preservatives—became dominant, relegating sourdough to some artisanal bakeries.

[1] Sourdough, an ancient bread on a modern table (photo © Geraud Pfeiffer | Pexels).

[2] Sourdough can take its place at every meal of the day: breakfast, lunch, and snacks (photo © Vicky Ng | Unsplash).

[3] Homemade sourdough starter. Here’s how to make it from scratch using only flour and water. You can also purchase ready-made starter (photo © King Arthur Baking).

[4] Avocado toast deserves sourdough bread (photo © Polina Tankilevich | Pexels).

[5] Goat cheese is spread on sourdough and topped with roast beef, sautéed mushrooms, and fresh arugula. The stack gets a drizzle of balsamic reduction (photo © ACE Bakery).

[6] A delicious open-face sandwich: smoked salmon, burrata, and marinated tomatoes with a chiffonade of basil (photo © Emine Bakirci | Pexels).

[7] We love this sandwich of porchetta and melted truffle cheese on toasted sourdough (photo © Veldhuyzen Cheese).

[8] Sourdough is also made in round shapes, called boules (French for ball). The shape isn’t right for sandwiches or toast, but the wedges are great in a bread basket, served whole at the table for diners to manually pull apart, enjoyed with cheese, etc. (photo © Jens Meyers | Unsplash).

Sourdough came to America with European immigrants, but it became the leading bread in San Francisco with the 1849 California Gold Rush.

Miners and settlers kept starters alive in tin pails and even wore them around their necks to keep them warm. The term “sourdough” even became slang for experienced prospectors.

French bakers brought sourdough techniques to Northern California during the Gold Rush (1848–1855), and the bread remains part of the culture of San Francisco, where it has been in continuous production since 1849.

Some bakeries can trace their starters back to those days!

San Francisco’s unique fog and local strain of Lactobacillus sanfranciscensis even gave the bread its signature San Francisco tang—more distinctly sour, especially in its aroma and finish.
 

[10] You can now find sourdough in many supermarkets (photo © Good Eggs).
 
 
4. SOURDOUGH TODAY

Thanks to the artisan food movement in the U.S., founded in the 1970s and fully matured in the 1980s, sourdough has undergone a revival. Now, most of us can enjoy it whenever we like—for toast, sandwiches and in the bread basket.

During the COVID-19 pandemic (2020-2023), home sourdough baking exploded as people had time to nurture starters. This led to a global “sourdough boom.”

From artisanal bakeries to fine restaurants to the commercial varieties on supermarket shelves, you aren’t far from a loaf.

If you haven’t had sourdough bread recently, today’s the day!
 

[11] Before sourdough starter, all bread was flat (photo © The Nibble).
 
 
5. THE HISTORY OF BREAD: BEFORE & AFTER SOURDOUGH

The earliest foods made from grain were gruel and porridge.

Before anyone baked bread of any kind, mankind gathered wild cereal grains (and later cultivated grains). Crushed or ground grains were boiled or simmered in water—the easiest and most fuel-efficient way to make tough, fibrous wild grains digestible.

• Gruel, a thin, drinkable/pourable cereal soup. It may contain less grain relative to the cooking liquid.
• Porridge, a thicker dish made by cooking grains, cereals, or other starchy foods in water or milk. It’s usually eaten with a spoon.
• Parched or roasted grains were made by tossing whole grains over coals or in dry pots so the husks could be rubbed off and the grain chewed directly.

 
 
The First Breads Were Flatbreads

When people began cooking grain pastes on hot stones, in glowing hearth embers, beneath hot ashes, or on early griddles, the result was unleavened flatbread.

Antiquity

• In 2018, archaeologists working at the Shubayqa 1 site in northeastern Jordan discovered charred breadcrumbs dating back roughly 14,400 years—predating the dawn of agriculture by several thousand years. Microscopic analysis showed that Natufian hunter-gatherers had ground wild cereals (wild wheat and barley) and club-rush tubers into flour, mixed them with water, and baked the paste into thin, unleavened flat cakes on heated hearth stones.
• Without leavening, a thick mass of flour and water will not rise. If that unleavened dough is baked thick, the outside burns while the inside remains dense, gummy, and raw.
• Thus, thin flatbreads (or small, flat ash-cakes) were the only practical way to cook dough through evenly.

 
 
Classical Antiquity to Middle Ages: Beer-Barm and Ale-Leavened Bread

• As recorded by Pliny the Elder in ancient Gaul and Iberia, brewers realized the foamy scum skimming the top of fermenting beer—known as barm—could leaven bread much faster than a standard sourdough starter.
• Barm-leavened loaves lacked the pronounced lactic and acetic acidity of traditional sourdough, yielding milder, sweeter, and airier breads.

 
 
Ancient to Imperial China: Steamed Breads

In East Asia, where wheat was less suited to dry hearth baking and firewood was often scarce, leavened doughs were cooked over boiling water rather than in ovens.

This produced soft, crustless, cloud-like breads such as Chinese mantou (plain steamed buns), baozi (filled steamed buns), and various Asian steamed flatbreads.
 
 
Middle Ages to Renaissance: Enriched Breads and Early Pastry Doughs

• Bakers began adding fats, dairy, and sweeteners to leavened doughs to create soft, tender loaves for royalty and festive occasions.
• This gave rise to brioche in France, challah in Jewish culinary traditions, panettone and pandoro in Italy, and stollen in Germany.
• The introduction of egg and butter emulsions transformed dense bread crumb into pillowy, cake-like structures.

 
 
Late Middle Ages to Early Modern Era: Boiled-Then-Baked Breads

A technique originating in Central and Eastern European Jewish communities, dough was shaped into rings, briefly poached in boiling water to gelatinize the surface starch, and then baked.

This method locked in interior moisture while creating a dense, chewy interior and a glossy crust, producing bagels, bialys, and bubliks, alongside the lye-dipped German pretzel family.
 
 
Late 18th to Mid-19th Century: Chemically Leavened Quick Breads

The discovery of pearl ash (potassium carbonate), followed by baking soda and baking powder in the 19th century, made biological fermentation optional for leavening.

Batters and soft doughs could rise instantly upon reacting with acid and heat, enabling the creation of Irish soda bread, American cornbread, biscuits, scones, and tea loaves.
 
 
Mid-to-Late 19th Century: Commercial Yeast Breads and Vienna Bread

In the mid-1800s, the isolation and mass production of pure Saccharomyces cerevisiae (compressed and dry baker’s yeast) revolutionized baking.

Combined with Hungarian roller-milling that produced ultra-refined white flour and Austrian steam-injected ovens, bakers developed Vienna bread.

This process laid the groundwork for the modern French baguette, sandwich loaves, and consistent, predictable daily bakery output.
 
 
Mid 20th Century: Industrial and Continuous-Mix Sandwich Breads

The invention of the Chorleywood Bread Process in the U.K. in 1961, and similar automated high-speed mixing methods in the U.S., introduced ultra-soft, uniform, mass-produced sliced white breads, such as Pullman loaves and Wonder Bread.

These relied on high-energy mechanical dough development, commercial enzymes, and oxidizers to bypass bulk fermentation entirely in under a few hours.
 
 
Late 20th Century: The Artisan Revival and Ancient Grain Renaissance

In the 1970s and 1980s, a strong cultural backlash against hyper-processed, flavorless industrial white bread took hold across Europe and North America.

• Pioneered by figures like Lionel Poilâne in Paris, Steve Sullivan (Acme Bread) and Alice Waters in California, and bread educator Peter Reinhart, bakers rediscovered slow-fermentation techniques, wood-fired hearth ovens, and wild sourdough cultures.
• Alongside this movement came the return to heritage and ancient grains—such as spelt, einkorn, emmer (farro), and stone-ground whole wheat—restoring crust, chew, complex acidity, and nutritional depth to daily loaves.

 
 
21st Century: The Modern Era, Sourdough Globalism, Inclusivity, and Science

In the 21st century, bread baking became both a high-science discipline and a widespread domestic art.

• Advances in microbiology demystified the precise interactions of wild yeasts, lactic-acid bacteria, and gluten networks, popularized by influential bakers like Chad Robertson (Tartine) and modernist baking laboratories.
• Simultaneously, increasing awareness of celiac disease and digestive sensitivities drove two parallel revolutions: sophisticated, high-quality gluten-free leavened breads using alternative starches (tapioca, millet, rice, and sorghum), and a deeper appreciation for long sourdough fermentations, which break down phytates and partially digest gluten proteins for easier digestion.
• The global COVID-19 lockdowns of 2020 cemented sourdough baking as a universal domestic phenomenon, connecting millions of modern home bakers directly with humanity’s oldest culinary tradition.

 
 
The Full Circle

Bread’s ten-thousand-year evolution has brought us full circle.

• Humanity began with wild grains ground between stones, cooked over open fires as humble flat cakes.
• Across millennia, we learned to harness invisible airborne yeasts, engineered soaring masonry ovens, and eventually industrialized the loaf into perfect, uniform slices of shelf-stable convenience.
• Yet, after achieving the pinnacle of automated speed, modern bakers and eaters have passionately returned to the beginning.
• Today’s most prized loaves look remarkably like those of antiquity: flour, water, salt, and time, leavened by living cultures and baked with a dark, crackling crust.
• From prehistoric ash-cakes to the neighborhood bakery’s sourdough boule, bread remains what it has always been—the simplest, most enduring cornerstone of human civilization.

 

[12] Snack time: artisan sourdough, whipped goat cheese spread, fresh figs, honeycomb, and walnuts (photo © Stockcake).
 

 
 
6. NAMES FOR SOURDOUGH IN 19 COUNTRIES

In English-speaking countries, of course, it’s sourdough. Travel elsewhere, and here’s what sourdough is called.

________________
 
*Communal ovens were long the practice in ancient societies through medieval Europe, for a combination of practical, social, and economic reasons. Baking bread requires a lot of heat and fuel, and it was inefficient for each household to fire its own oven daily. A large shared oven conserved fuel and many loaves could be baked in a single firing. Plus, ovens were expensive and labor-intensive to build and maintain. Communal ovens allowed whole neighborhoods or villages to share one well-built structure instead of many small, fragile ones.

The large, sturdy oven produced more consistent bread than if each household baked independently in a small one.

Experienced bakers often ran the communal ovens. In Rome, for example, the professional guild bakers (pistores) ran many of the city’s public ovens.

The communal oven was also a gathering place where housewives or servants could gather and socialize.

Among all the loaves, how did you know which loaf was yours? Households fashioned a stamping device from clay, and pressed their “brand” into the raw loaf.

†Barm was likely first used in Ancient Egypt, circa 3,000 to 2,000 B.C.E., the time when brewing and baking overlapped. It was first documented in Europe in Roman accounts curing the 1st century C.E., which noted its use in Gaul and Iberia.

In Northern Europe from approximately the 9th through 15th centuries, the use of barm became common wherever ale was brewed. The Old English word beorma (from Proto-Germanic bermô, meaning yeast or leaven) is the root of the word barm.

With the isolation of pure Saccharomyces cerevisiae and the broad availability of commercial compressed yeast at the start of the 20th century. Slower and less consistent than commercial yeast was faster and more consistent. Even those dishes that retain the word “barm,” such as Irish barm brack (a fruit bread) and barm cake (soft rolls from Lancashire and Greater Manchester) use commercial yeast.

‡Real Bread Week was held Saturday, February 21st through Sunday, March 1st, 2026. The 18th annual celebration will take place Saturday, February 20th through Sunday, February 28, 2027th.
 
 

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