This example presents two maps side by side: a world basemap using TopoJSON data from world-atlas and a US choropleth showing education levels (percentage of adults with a bachelor’s degree or higher). The world map uses d3.geoNaturalEarth1 and d3.geoPath to render neutral country boundaries, while the US map joins CSV data with FIPS codes from us-atlas via d3.csv, applies a sequential PuBuGn color scale, and includes an interactive tooltip for state values.