most likely just another state but especially if it is not called an international border
What state borders to the north of where? There is not enough information.
California is North of California's southern border, and Oregon is North of California's northern border.
The US state of South Dakota is the southern border of North Dakota.
None. A border defines the boundary of a state therefore no state will cross the border of another state.
Tennessee is on North Carolina's western border
Tennessee and North Carolina
The US state of Montana has an eastern border with North Dakota and South Dakota.
Alaska
North Dakota and South Dakota border Minnesota to the east.
Illinois is bordered by Wisconsin to the north.
Mississippi is bordered by Tennessee to the north.
Alaska