While most rivers that separate states/countries are usually cut right down the middle, not so with the Connecticut River between Vermont and New Hampshire. No, apparently, New Hampshire won the game of rock-paper-scissors and got most of the river all to itself, and even some land on the Vermont side. Seriously, check it out on Google Maps -- it's crazy.
So when the Vermont town of Brattleboro began to grow, and bridge trusses/footings were extended out onto the river to support new infrastructure, they ended up crossing state lines. As a result, a part of the Whetstone's interior resides in each state and a bright yellow line on the floor marks the border. While it’s a Vermont establishment for tax purposes, you can still have a drink in New Hampshire while you’re there.