This choropleth map visualizes US state populations using a sequential YlGnBu color scale. State boundaries are rendered as SVG paths via d3.geoPath, populated with data loaded from TopoJSON (us-atlas). A tooltip displays state names and population values on hover. The map uses d3.geoAlbersUsa for projection and d3.scaleSequential for color mapping. A legend with a linear gradient and d3.axisBottom provides a scale for interpreting the population values in millions.