The largest seawater desalination plant operating in the United States is the Claude "Bud" Lewis Carlsbad Desalination Plant, located in San Diego County, California. This massive facility produces approximately 50 million gallons of high-purity drinking water every single day through advanced reverse osmosis technology, supplying roughly 10 percent of the total water demand for the San Diego region and serving as a major milestone in drought-resilient municipal water infrastructure.