Marshall's discovery was almost accidental. John Sutter had hired him to build a sawmill on the American River to supply lumber for his expansive agricultural empire in the Sacramento Valley. The mill's construction required deepening the tailrace to improve water flow, and it was during this routine maintenance that Marshall spotted the metallic flakes that would change everything. Initially skeptical, Marshall collected several pieces of the mysterious metal and conducted crude tests, including hammering and boiling, which convinced him that he had indeed found gold.