brew install p7zip cairo pixman optipng gdal npm install
If the installation of the node-canvas module fails for you, you can try this after the above:
PKG_CONFIG_PATH=/opt/X11/lib/pkgconfig npm install canvas
See the wiki for more install help.
To make the above PNG for the entire United States, type
Make a TopoJSON file for a specific state:
Make a Shapefile for a specific state: