centerZoom - Automatically centers and scales your map to its container, and returns your map’s outer boundaries in case you want to draw them.
drawOuterBoundary - Uses the boundary returned from
centerZoom to draw a boundary around your whole map.
drawPlaces - Draws place names, if your topojson has places.
drawSubunits - Draws subunits.
colorSubunits - Colors the subunits.
This map uses a Mercator projection, and the colors are generated from
d3.schemeCategory20. For a tutorial on converting Geojson to Topojson and for finding the coordinates of major cities, see this tutorial.