On the island of Molokai:
Kalawao County can be reached by sea or by mule train but if you intend to visit, leave your children behind. State law prohibits anyone under sixteen from living in or visiting the second least populated county in America.
Kalawao County is Kalaupapa Peninsula, on the north coast of the island of Moloka’i. The small peninsula of Kalaupapa is isolated from the rest of Moloka’i by sea cliffs over a quarter-mile high â€” the only land access is a mule trail.
Wikipedia’s entry for Kalawao County.