A piece of New Brunswick in Nova Scotia

[ghYHZ]

There is no border depute between New Brunswick and Nova Scotia but a piece of NB has ended up on the NS side of the Missaguash River due to an 'Oxbow' in the river that was straightened.

I've heard of the oxbows along the Mississippi causing one states boundaries to be within the other...but the first time I'm aware of it here. Any other provinces with boundaries within the other?

https://www.cbc.ca/player/play/1964298820001

[Alps]

TIL there's a third border crossing there, just north of 104. Dirt road with a Bailey bridge.

[webfil]

I've heard of the oxbows along the Mississippi causing one states boundaries to be within the other...but the first time I'm aware of it here. Any other provinces with boundaries within the other?

I know of similar cases for international borders. The boundaries on Saint John and Saint Francis rivers between Québec and Maine have minor discrepancies due to meanders becoming oxbows, but Hall river between Québec and New Hampshire is quite something. The former borders were delimited in 1842 (Webster-Ashtonbury) while the latter is older (1783; Treaty of Paris), thus the greater shapeshift.

EDIT : I just recalled that rivers changing courses are a the very source of the border dispute between Croatia and Slovenia, along the Mura and the Dragonja.

[cbeach40]

Well, there's always this one...
https://en.wikipedia.org/wiki/Border_between_Quebec_and_Newfoundland_and_Labrador

[Alps]

Well, there's always this one...
https://en.wikipedia.org/wiki/Border_between_Quebec_and_Newfoundland_and_Labrador

Quebec isn't a sovereign nation so they just have to put up and shut up.

[oscar]

Quebec isn't a sovereign nation so they just have to put up and shut up.

Only they aren't shutting up, almost a century after Great Britain's Privy Council decided against Quebec on its border dispute with Newfoundland/Labrador (then not part of Canada, but a separate dominion within the British Commonwealth). The official 2020-2021 Quebec road map I purchased earlier this month from a visitor centre SW of Quebec city (cost C$5.20, with sales tax) prominently shows the border that Quebec originally claimed, with only microscopic markings of the "non-definitive" Privy Council border shown on the map cbeach40 posted, which the rest of the world treats as the real border.