This example shows a choropleth of income levels by zip code overlaid on a Google Map, centered on Virginia’s Northern Neck region. A Google Maps KmlLayer fetches a remote KML file containing the geographic boundaries and income data, while the map itself uses the TERRAIN map type for topographical context. The code directly integrates Google Maps’ JavaScript API with d3.v3, using d3 only to select the map container; no d3-specific data joins or scales are used for rendering. The visualization relies entirely on the KML file’s styling to color-code regions, with no additional D3 drawing or interaction logic.