Saleratus was an early form of baking powder first sold in the early 19th century. Pearl ash (introduced in 1790), saleratus (introduced in 1840), or bicarbonate of soda are alkali chemical agents used to make breads, cakes, and biscuits rise and form a light final product. Around 1850, bicarbonate of soda was combined with an acid, usually cream of tartar, to create baking powder, the leavening agent still used today. With these products, home cooks could make baked products much quicker and easier. Yeast, used to leaven breads for thousands of years, was no longer required to make baked products light.
From The Missouri Cookbook, 1887.