North Dakota Constitution Art. IV, § 2

The legislative assembly shall fix the number of senators and representatives and divide the state into as many senatorial districts of compact and contiguous territory as there are senators. The districts thus ascertained and determined after the 1990 federal decennial census shall continue until the adjournment of the first regular session after each federal decennial census, or until changed by law.

The legislative assembly shall guarantee, as nearly as is practicable, that every elector is equal to every other elector in the state in the power to cast ballots for legislative candidates. A senator and at least two representatives must be apportioned to each senatorial district and be elected at large or from subdistricts from those districts. The legislative assembly may combine two senatorial districts only when a single member senatorial district includes a federal facility or federal installation, containing over two-thirds of the population of a single member senatorial district, and may provide for the election of senators at large and representatives at large or from subdistricts from those districts.