Horsford was a Harvard professor who, in 1856, began his experiments to develop a leavening agent that was not yeast-based.  A leavening agent causes a chemical reaction – it creates gas bubbles that softens doughs and batters, increasing their volumes and lightening their texture.  Horsford wanted to invent a powder leavening agent that would release carbon dioxide, raising the dough but without the taste and odor of yeast fermentation.

Horsford set up his chemical works in the Rumford section of East Providence.  He tested a number of substances before settling on a combination of calcium acid phosphate, sodium bicarbonate and, eventually, corn starch.  His “recipe” was that one teaspoon of the leavening agent should raise a dough/batter of one cup of flour, one cup of liquid and one egg.   He first marketed this new product as Horsford’s Yeast Powder.  He was very successful.  In 1869, because he wanted to package the powder in a tin can, he added corn starch to prevent moisture.  Over the years, bakers throughout the world have become familiar with the iconic red can of Rumford Baking Powder, whose formula has remained unchanged in 1869.  In 2006, Rumford Baking Powder was designated a National Historic Chemical Landmark.  Rumford Baking Powder remains the leading baking powder in the United States.