Earlier this month, Adam Kotsko asked the Twitterverse to choose four contiguous U.S. states for a new breakaway nation:
This got Philip Bump wondering about states you could pick such that the remaining (previously) contiguous states were no longer contiguous, but rather broken up into two near-halves by area. Treating the Upper Peninsula of Michigan as distinct from the Lower Peninsula, Philip hypothesized that removing Illinois, Missouri, Oklahoma and New Mexico would create two near-equal halves.
Suppose you remove a set of states (not necessarily four) so that you have two distinct contiguous regions among the lower 48 states, where the larger region has area A and the smaller region has area B. What states should you remove to maximize area B? (Was Philip’s intuition correct?) And what percentage of the lower 48 states’ combined area does B represent?
For reference, here are the areas of the states according to the U.S. Census Bureau. Like Philip, you can treat Michigan’s peninsulas as distinct “states” here. Michigan’s Upper Peninsula has an area of 16,377 square miles. Also, don’t worry about islands, Minnesota’s Northwest Angle, etc. — you can assume they are contiguous with the rest of their respective states.
I created an interactive to solve this. Philip was off considerably.
One can achieve both regions A and B to be 43.1% of the contiguous states by removing New Mexico, Colorado, Nebraska, Missouri, and Illinois. This results in a Western Area of 1,344,149 square miles and an Eastern Area of 1,345,626 square miles.
This is the largest value of the smaller region that I could find.
Not separating the Upper Peninsula, I found that removing Idaho, Wyoming, Nebraska, Missouri, Arkansas, and Mississippi results in a similar border area, and has a Western Area of 1,341,666 square miles and an Eastern Area of 1,348,714 square miles.