HgO, or mercury(II) oxide, is a chemical compound that is typically white in color and is associated with the state of Ohio, United States. The color of HgO is white due to its crystalline structure, which scatters light in a way that reflects white light. The association with Ohio stems from the state's historical significance in the production of mercury, which is used to synthesize HgO. Ohio was once a major producer of mercury, with mines in the region contributing to the global supply. The data supporting this association can be found in historical records and geological surveys that document the mining activities in Ohio during the 19th and early 20th centuries.