This example displays a map of Oklahoma’s counties, drawn as individual gray paths with darker borders between counties and a thicker outline around the state. Hovering over any county turns it orange. The map loads county geometries from a TopoJSON file and renders them as SVG using `d3.geo.path` with a null projection, meaning coordinates are used directly. The code relies on `topojson.feature` to convert the Topology into GeoJSON and `topojson.mesh` to draw the county and state boundary lines.