This visualization displays EPA air quality monitoring sites across the contiguous United States, where each circle represents a sample location and its radius encodes the ozone AQI value. The map uses React with the `d3.geoAlbersUsa` projection and `d3.geoPath` to render state boundaries and interiors from a US Atlas TopoJSON source. EPA station data, loaded via `d3.csv`, is positioned by geographic coordinates, with circle sizes scaled using `scaleSqrt` to give visual weight to higher AQI readings.