Neb. Rev. Stat. § 22-108

The county of Boyd is bounded as follows: Commencing at a point in the middle of the main channel of the Niobrara River intersected by the range line between eight and nine west; thence north on said range line to the middle of the main channel of the Missouri River; thence up the main channel of said river to a point intersected by forty-third north parallel; thence west on said parallel to a point intersected by the range line between ranges sixteen and seventeen; thence south on said line to a point in the middle of the main channel of the Niobrara River; thence down the main channel of said river to the place of beginning.