This example shows U.S. Environmental Protection Agency air quality data as a bubble map, with circles representing sites and sized by their AQI value over a geoAlbersUsa projection rendered with d3.geoPath. The visualization combines a state-atlas overlay with data-driven circles, and also includes a date histogram that bins the same dataset by month to show average AQI trends. It uses React hooks to load the data via d3.csv and the U.S. Atlas TopoJSON, while d3.scaleSqrt, d3.bin, and d3.scaleTime handle quantitative scaling and temporal aggregation.