Dialing Around: How Rotary Phones Shaped the Distribution of US Area Codes [telecom]

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These days, our phones tend to keep track of these things for us, but back when most people memorized numbers, they didn't always make sense. The first digits of zip codes and social security numbers assigned in the United States ascend from east to west, starting low around the original American colonies and going up from there. Interstate numbering also follows east/west as well as north/south patterns. So how did the country wind up with such an odd layout of area codes? For context, we need to revisit the earlier days of the phone network.