According to one legend, Christopher Columbus was the first person to bring European sourdough to America.

He carried with him a crock of bread starter—a fermented product that still takes the place of commercial yeast in artisanal loaves today. But the American history of sourdough bread really starts in San Francisco during the California Gold Rush.

That’s when the city went from a small outpost of uncertain allegiance (it was Mexican for a long while) to a relatively big city as it was flooded with miners looking to get in on the action. Along with a predilection for gambling, which concerned townsfolk, the miners brought with them or made bread starters. The starters were so important that they would cuddle them on cold nights so the yeasts and bacteria that made them viable didn’t die, writes Avital Ungar for San Francisco Travel. Same goes for miners in Alaska.

But in San Francisco, they found that the bread they made tasted different—more sour, chewier, tangier—than it had back home. The San Francisco sourdough got its official beginning with the opening of Boudin Bakery in 1849, the second year of the rush.

“Local bakers swore that no one could reproduce it outside a 50-mile radius of the city,” write Patricia Gadsby and Eric Weeks for Discover Magazine. “When they gave dough to bakeries elsewhere, it inexplicably lost its ‘sour.’” That taste comes from the lactobacilli in the starter, they write.

In the 1970s two researchers set out to find the truth. What Frank Sugihara and Leo Klein found was that there was a bacteria in the San Francisco starter that hadn’t been catalogued before. The researchers initially suggested the name L. sanfrancisco, and it was eventually named L. sanfranciscensis, Gadsby and Weeks write.

But in spite of its name, the bacteria isn’t unique to the San Francisco region: it has since been found France and Germany, among other places. Some bakers still insist that true San Francisco sourdough has to be made there, where the climate and the wild yeasts in the air are specific to the region. Others say the exact ratios of different kinds of yeasts and lactobacilli don’t matter much at all, and it’s more about technique.

“I think you can make San Francisco sourdough pretty much anywhere,” Sugihara told Discover. As one of the first to study it, he’s in a position to know.

As for Columbus, though he may have been hoping for a slice of wheat toast (who isn’t?) the bread that first took off among European settlers in the Americas was cornbread, according to Marne Stetton in Saveur. After all, wheat wasn’t even grown in what would become the United States for more than a hundred years, and yeast wouldn't be produced commercially until 1868.