This visualization maps Air Quality Index (AQI) data across the United States, displaying each monitoring site as a circle sized proportionally to its AQI value. The map uses a `geoAlbersUsa` projection and `geoPath` to render state boundaries from TopoJSON, while circles are scaled with `scaleSqrt` on a dataset from a CSV file. The React-based interface integrates D3 v5 for data loading and map rendering, with SVG elements providing a clear, interactive view of regional air quality variations.