This example displays a choropleth map of poverty rates across U.S. counties, using a sequential blue color scale to encode percentages from 0 to 100. It loads county boundaries from the TopoJSON `us-10m.v1.json` dataset and merges them with CSV data containing poverty estimates. The map is rendered as SVG paths via `d3.geoPath` with an AlbersUSA projection fit to the viewport, while `d3.scaleSequential` with `d3.interpolateBlues` determines each county’s fill color.