Technically the fewest number of county borders is zero, a situation that occurs frequently on islands. As an example, individual Hawaiian islands are not split by county borders with the exception of Molokai, found mostly in Maui County but also cradling the minuscule Kalowao County – the smallest county in the United States – on its northern shore. Hawaii seems to be a good place to start exploring this situation further.
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By definition Islands are noncontiguous unless someone decides to draw an artificial line across it, like Molokai. Otherwise it will be self-contained and won’t have any borders. So let’s take a look at these islands and decide which one of the remaining three counties might be the best candidate for “fewest” borders. Honolulu County is composed mostly of Oahu but also administers a string of minor islands, shoals and reefs stretching hundreds of miles northwest to Kure. Kauai County comes closer with just the island of Kauai and its nearby neighbor, Nihau. That leaves Hawaii County, composed solely of the “Big Island” of the same name, as a possible candidate. It is a county, it is self contained, and it is composed of a single chunk of earth surrounded by water.Other candidates on the mainland should also be considered. The Massachusetts counties of Dukes (Martha’s Vineyard) and Nantucket spread over open water but both contain minor islands along with their more famous brethren. Island County, Washington also comes close with two islands: Whidbey and Camano. Likewise Alaska’s Kodiak and Aleutian counties along with those that line the Inside Passage spread across open water but all contain numerous islands. If we must split hairs and say which county in the United States has the fewest borders, Hawaii County, HI would be as good a candidate as any. However this is really just a trivia question, and a pretty lame one at that. Too many geography quizzes depend upon Hawaii as a stumper. Things get more interesting on the mainland.