After my initial data collection, I found I had that I had to modify my approach to improve the network. First of all, I had to add some nodes for certain highway-to-highway connections, especially those that occurred in remote areas. I also had to include some cities that had multiple Interstate highways passing through because they weren’t always listed on each route. Finally, I added a few non-Interstate roads where I thought it made sense, including Alaska (which doesn’t actually have any Interstate highways) and eastern Canada, which has a major highway called the King’s Highway or Ontario Highway 401 linking Toronto and Montreal to key American cities.
Here is the result … click on the picture to get to a fully interactive version.
The size of the nodes is related to the estimated population of the city/destination and the color represents Census division (plus Canada). You can kind of see a rough outline of the U.S., with the Midwest roughly in the center of the diagram (in orange) and the two coasts wrapping around on either side. Hawaii and Alaska float alone at the edge and the Florida penninsula (in the South Atlantic, in red) protrudes out toward the bottom of the chart.