https://www.scientificamerican.com/article/99-percent-of-families-prefer-yeasty-bread/

“Within the past 10 years there has been a revolution in making bread. The ancient leaven bread was made by the dough being left in a warm place till it began to ferment. The chemical progress is the starch into sugar, then carbonic acid and alcohol, which forms between the particles of flour and swells them up. But great care was required in the operation, lest it be decomposed, and therefore the modern process by yeast is much more preferable. Besides yeast in making bread, we have had ‘baking powders’ and ‘self-raising flour,’ and such, and 99 families in 100 use some of these.”

—Scientific American, February 1860