This interactive map displays all US states and their counties using D3 v4 with SVG rendering. The visualization loads TopoJSON geographic data for county and state boundaries, along with CSV files that provide names for both administrative levels. Counties are rendered as white polygons with grey borders, while state boundaries are highlighted with a thick steelblue stroke. Hovering over any county turns it red, thickens its border, and displays a tooltip showing the county name and state, positioned to follow the mouse cursor. The map uses a queue to load the three data files, and a geoPath projection renders the TopoJSON features.