A choropleth map of the United States colors individual states by population, using a threshold color scale that ranges from light yellow to dark amber. The visualization loads US state boundaries from the us-atlas TopoJSON file and renders them as SVG paths via d3.geoPath with an Albers USA projection. Population values are mapped to FIPS codes using a JavaScript Map, and the d3.scaleThreshold assigns fill colors based on population brackets. Hovering over a state triggers a native SVG title tooltip displaying the FIPS code and population figure.