IDK if pretty much everyone can exclude Florida and Texas, the second and third most populated states. (Or I suppose you could be excluding the Northeast Corridor instead of Florida)
I'm no expert on USA but looking at a map Florida is very obviously on the east coast, and the entire peninsula is only slightly wider than GP's 100 miles.
Touche, I was thinking of it more as 100 miles in length, not 100 miles in width running all the way down the coast, but your interpretation seems more correct.
Take a 100 mile strip down the east coast and the west coast. Add Chicago. That's pretty much everyone.