This choropleth map visualizes educational attainment across U.S. counties, using d3.scaleThreshold with a green color scale to encode the percentage of residents with bachelor’s degrees or higher. County boundaries are rendered as SVG paths via d3.geoPath and a geoAlbersUsa projection, with data loaded from FreeCodeCamp’s TopoJSON and JSON datasets. The map supports pan and zoom through d3.zoom, and includes a color legend built with reusable custom D3 components. Hovering highlights individual counties by changing their fill color.