What was optimized when New York was assigned the area code 212? We share a classroom activity were students reason their way to the patterns underlying the initial set of North American area codes. We observe the format of the original set of allowable area codes and determine the number of possible area codes in that format. We also seek connections between the numbers and the geography of North America that led to the assignment plan. The history of phone system technology and our phone number formats plays a role in an interesting optimization problem hidden underneath a seemingly random assignment of numbers to places.
