The GenOn Potomac River Generating Station, a 63-year-old coal-fired power plant on the Potomac River, north of Old Town Alexandria, permanently shut down this week. The plant closed after dogged efforts by local residents and environmental activists, who argued the 482-megawatt plant was harming local air quality and endangering residents.

The Washington Post called the plant the “largest single source of air pollution in the Washington region.” The plant’s smokestacks emitted fine particulate matter and sulfur dioxide, occasionally at levels that could temporarily harm sensitive individuals, according to a recent air quality study.