This example displays a choropleth map of Maryland counties from the US Atlas TopoJSON data, with hover highlighting that turns each county red and logs its FIPS ID to the console. It uses d3.geoPath to render SVG paths of county boundaries, while a threshold color scale applies a sequential OrRd scheme. The county borders are drawn as a separate white mesh for contrast. The code loads the topojson feature collection and removes non-Maryland tracts, though the data lacks population values, so the color encoding remains visually uniform.