This example displays a choropleth map of the United States, showing state boundaries with a white fill and black strokes. Upon hovering over a state, its fill color changes to goldenrod via a CSS `:hover` rule. The map is rendered as an SVG using D3 v5 and the topojson library, specifically employing `d3.geoPath` with the `geoAlbersUsa` projection. Data originates from the `us-atlas` counties-10m JSON, with state features extracted via topojson's `feature` function.