This map of US states categorizes each region with a distinct color: the Northeast in blue, the Midwest in teal, the South in green, and the West in light blue. It uses D3 v5 with TopoJSON to load and render the states, applying `d3.geoPath` to draw each selected region. The code filters state geometries by region sets and merges them separately to color the paths via CSS classes. Data comes from the US 10m TopoJSON file hosted on d3js.org.