My best guess would New Jersey and Maryland, separated by Delaware. However, Massachusetts and Maine (separated by the New Hampshire coastline around Portsmouth) must run that pretty close. I’d have to look at a map to decide!
The answer I was going for was New York and Rhode Island. Fisher Island, which is part of New York, is less than two miles off the shore of Rhode Island.
But I may have to concede this one. I’ve always thought of Delaware and New Jersey as having a border but they are separated by the Delaware River. If the bridge that connects the two states doesn’t count as a shared border then they are separated but closer than New York and Rhode Island.
My typo was that in post #10 I meant to write “New Jersey / Maryland, separated by Delaware”, as I had previously done in post #7. I would agree with you that New Jersey and Delaware share a border (the Delaware River) and thus does not qualify.
My misunderstanding, however, is that I thought that by “not touching” you meant that another state intervened, as in the case of my (and tomndebb’s) examples. By my understanding of your question I would say that NY / RI doesn’t qualify, since I think that there is a NY / RI border but it’s in the Long Island sound.
If we now say “aquatic borders don’t count” then I’ll have to rethink. Fisher’s Island NY certainly sounds like it would be hard to beat.
I was just about to point out that you’d be conceding to an unintentional submission by me, when I decided to actually take a look at a map!
It turns out that there are two places where DE has land on the eastern bank of the Delaware River. One of them is in the Killcohook National Wildlife Refuge (most of which is in NJ). Thus, DE and NJ share a land boundary even if you don’t count the bridge, and the typo is disqualified.
If water boundaries count, then NY / RI are disqualified and I resubmit MD / NJ which have about 11 miles of DE separating them. NJ / CT are also about 11 miles apart (NY intervening), and MA / ME about 14 miles (NH being in the way).
If one redefines the problem as “shortest driveable distance” then MA/ME wins it as it’s a straight shot up I-95 through NH.