On Jul. 31, 1790, the inventor Samuel Hopkins was awarded the first U.S. patent for a new method of making potash and pearl ash.

Potash, later termed potassium carbonate, was used as a fertilizer, as a detergent to clean fibers in textile manufacturing, and as an ingredient in soap. Pearl ash was a more refined material used in glassmaking, to make saltpeter for gunpowder, and as a leavening agent in baking (baking soda and baking powder were not invented until the 1840s).

Both potash and pearl ash were manufactured by burning wood, mixing the ashes with water, and then boiling off the liquid in large iron kettles, typically at the edges of newly cleared fields. They were valued exports in the colonial and early republic periods.

After receiving the nation’s first patent, Hopkins initiated the nation’s first patent licensing program.

The patent, for a process of making potash, an ingredient used in fertilizer was signed by President Washington. The original document is in the collections of the Chicago Historical Society.