This choropleth map colors U.S. counties to visualize geographic data, with state boundaries drawn as white lines for contrast. The map is rendered as SVG using `d3.geoPath` to project TopoJSON geometry onto a 960×600 canvas. County and state shapes are styled via CSS classes, with the d3-scale-chromatic library available for color encoding. A small script sets a tooltip title on the label element, though the map itself does not display interactive data values.