Choropleth Map of County Data
A choropleth map displays the poverty rate for counties across the United States, with each county shaded according to its value. The visualization uses a threshold color scale with a green sequential scheme, and includes a legend showing the percentage ranges. The map is rendered as SVG using d3.geoPath and TopoJSON, with state boundaries drawn as a white mesh. Data is loaded from external JSON and CSV files, and colors are assigned via d3.scaleThreshold.