This is hilarious. There was a border dispute between California and Nevada. And because it was never resolved, apparently it is still ongoing.

https://en.wikipedia.org/wiki/Lake_Tahoe#Government_and_politics

When California was admitted to the union it's border was defined a certain way and later when Nevada was admitted it's border was defined in a different manner. At the time it was thought that these two methods were identical but when they actually went out to survey the border it turns out they are not. And because congress does not have the authority to change state lines I guess it is up to the states themselves to negotiate border disputes and both refused to give.