The Red River (of the North) forms North Dakota's eastern boundary with Minnesota.
Montana borders North and South Dakota,
There is no country which borders both North Dakota and South Dakota. North Dakota shares a border with Canada.
The US state which borders North Dakota on the west is Montana.
North Dakota borders Canada. North Carolina does not border Canada.
The US state of Montana's eastern borders are North Dakota and South Dakota.
North Dakota borders South Dakota. North Carolina borders South Carolina.
The US state of Minnesota borders North Dakota and part of South Dakota on their eastern borders and the US state of Montana borders North Dakota and part of South Dakota on their western borders.
South Dakota
The answer is South Dakota. Kentucky borders Tennessee to the north. South Dakota borders Nebraska to the north.
South Dakota borders Nebraska on the north.
The Canadian province of Manitoba borders both US states of North Dakota and Minnesota.
There is no one body of water which borders all of those states. The Missouri River travels through North Dakota and South Dakota, then borders Nebraska and Iowa and part of Kansas and Missouri before it travels through the state of Missouri and joins the Mississippi River. The Red River borders Texas and Oklahoma and then travels through Arkansas and Louisiana before it joins the Mississippi River. The Red River of the North borders North Dakota and Minnesota. The Mississippi River travels through Minnesota and borders Iowa, Missouri, Arkansas, and Louisiana.