A choropleth map of U.S. county unemployment rates colors each county with a blue sequential scale, using a quantize scale with nine bins from 1% to 10%. The visualization loads unemployment data from a CSV file and county and state boundaries from a TopoJSON file. The React app renders an SVG via D3’s `geoPath` projection, with state borders stroked in white and hover tooltips showing county names, state names, and exact rates.