Today we'll play with two data sources to triangulate on obesity in America. First, we will map out fast food restaurants using dots. Then, we'll employ some CDC Diabetes Atlas data to make a choropleth map inspired by this example.
This repository has a good collection of US map files, some of which have been *pre-projected* so that they are even more efficient. For those, you just need to use d3.geoPath() without a projection. In all files they have carefully simplified boundaries and verified that nation/state boundaries match up with the individual county edges.