This visualization pairs a world map with a U.S. choropleth map, drawing on D3.js v7. The world map uses the Aitoff projection via `d3.geoAitoff` and `d3.geoPath` with `topojson-client` to render country shapes. The U.S. map projects states using `d3.geoAlbersUsa` and shades them according to median household income, with a color legend and hover tooltips. A graticule grid overlays the world map. Both maps use SVG paths, and the income datapoints are embedded as CSV text. The title notes the U.S. map is a choropleth, with hover states revealing exact values.