This example shows a choropleth-style map of U.S. counties rendered as black filled shapes with subtle gray strokes. The visualization uses D3 v5’s `d3.geoAlbersUsa` projection and `d3.geoPath` to draw each county boundary, while the TopoJSON library’s `feature` method extracts county geometries from a remote US-atlas JSON dataset. County names appear as tooltips via appended `title` elements. Hovering over a county highlights it in black, though the fill remains unchanged. The map is displayed in an SVG container sized at 960 by 500 pixels.