This choropleth map displays U.S. state populations, with darker blue fills indicating higher population values and gray for states without data. It uses D3 v7 with `d3.geoAlbersUsa` projection, `d3.geoPath` for rendering, and `topojson.feature` to parse the us-atlas states-10m TopoJSON source. A `d3.scaleSequential` with `d3.interpolateBlues` maps population values to colors, while mouseover events update an HTML tooltip showing state names and population in millions.