What is the main setting in the novel, Wilder Girls?

All the events of this novel take place on Raxter Island, located off the coast of Maine, but there are several references to the mainland and this is the destination Hetty and Reese have in mind when they leave the island. This is also where the supply boats originate. The medical staff who briefly populate the visitor's center and who are trying to find a cure arrive on the island from the mainland.