This choropleth map visualizes poverty rates across U.S. counties, using a blue sequential color scale to encode the percentage of residents in poverty for 2021. County boundaries are rendered as SVG paths via `d3.geoPath()` from TopoJSON data, while color values are mapped from a CSV dataset joined by FIPS codes. The map includes a hover tooltip via SVG `<title>` elements, and missing data appears gray. It uses D3 v7, TopoJSON, and d3-legend for potential legend support.