US Airports Map
This map uses data on all US airports to display them all. The number of airports per state is used to create a choropleth map. The break points for the map are taken using quintiles on the number of airports per state.
The data for airports come from Data.gov, the link is broken and no longer working. The US States data comes from Mike Bostock at D3.
This map was made with Leaflet.js and the icons are from Font Awesome.
Extra Functionality
The extra functionality I added was the addition of making the icons go away when you zoom out so you can see the choropleth better.