2009.1.7 More geo-graphs: California counties

Well, the semester's long over by now and I'm recharged enough to want to forge ahead with multiple (I hope) items for the POIB. To start with is a new geographic investigation akin to the states graphs, namely a graph showing the counties of California and their shared borders. As before, each county is represented by a node that lies approximately at its centroid, and two nodes are connected by a line if their corresponding counties share a border. It'll be difficult to figure out which node represents which county unless you RLY know your California counties well:

California counties graph

But regardless of whether you're able to identify specific counties, there are some interesting things to see here. For instance, the pattern of large counties to the south and north and much smaller counties in the central Central Valley and Bay Area is very clear. Three counties of the Central Valley, Sacramento, Fresno and Kern, border eight other counties each, similar to Missouri, Kentucky, and Tennessee in the graph of the states. No other CA county has this many neighbors. In the case of Kern County, this high degree of adjacency is thanks in part to viewers like you its very large relative area, which allows for a lengthy perimeter as well. With Fresno and Sacramento Counties, it is more due to the irregular, extended shapes of the counties, which allow them to reach around to touch many others.

Another interesting feature revealed here (and that took some research with the topo maps at usgs.gov) is that there are three instances of Four Corners, that is, four counties coming together at a point. This is in contrast to the states, where there exists only the single Four Corners of Utah, Colorado, New Mexico, and Arizona. Following are the CA counties with Four Corners:

Here are the three regions in the graph that correspond to those Four Corners locations:

California counties graph with Four Corners locations highlighted

Kern County and Monterey County come within 1.2 miles of each other and thus of creating another Four Corners with San Luis Obispo and Kings Counties — indeed it looks just like a Four Corners until you're able to zoom in close.