Beginning at the point where the boundary line between the states of North Dakota and Montana intersects the eleventh standard parallel; thence east along the eleventh standard parallel to the southeast corner of township one hundred forty-five north, range ninety-eight west of the fifth principal meridian; thence north along the line between ranges ninety-seven and ninety-eight west to the northeast corner of township one hundred forty-eight north, range ninety-eight west, a point on the twelfth standard parallel; thence east along the twelfth standard parallel to the southeast corner of township one hundred forty-nine north, range ninety-four west; thence north along the line between ranges ninety-three and ninety-four west to the main channel of the Missouri River; thence in a northwesterly direction along the main channel of the Missouri River to a point where the boundary line between the states of North Dakota and Montana intersects the main channel of the Missouri River; thence south along the boundary line between the states of North Dakota and Montana to the point of beginning.