California Powder Works was the first American explosive powder manufacturing company west of the Rocky Mountains. When the outbreak of the Civil War cut off supplies of gunpowder to California's mining and road-building industries, a local manufacturer was needed. Originally located near Santa Cruz, California, the company was incorporated in 1861 and began manufacturing gunpowder in May 1864. For fifty years, it was a major employer in the county, employing between 150 and 275 men. The powder works was located on a flat adjacent to the San Lorenzo River, three miles upstream of Santa Cruz.