This map visualizes U.S. EPA air quality site data, plotting circles for each location with a radius that encodes the AQI value. A geospatial projection via `d3.geoAlbersUsa` and `d3.geoPath` renders state boundaries from a TopoJSON US Atlas, while the circle sizes are scaled using `d3.scaleSqrt`. The React components load CSV data with `d3.csv` and render the SVG elements, with hover effects on states and semi-transparent blue circles marking the sites.