Montana Constitution Art. V, § 14. Districting and apportionment

(1) The state shall be divided into as many districts as there are members of the house, and each district shall elect one representative. Each senate district shall be composed of two adjoining house districts, and shall elect one senator. Each district shall consist of compact and contiguous territory. All districts shall be as nearly equal in population as is practicable.

(2) In the legislative session following ratification of this constitution and thereafter in each session preceding each federal population census, a commission of five citizens, none of whom may be public officials, shall be selected to prepare a plan for redistricting and reapportioning the state into legislative districts and a plan for redistricting the state into congressional districts. The majority and minority leaders of each house shall each designate one commissioner. Within 20 days after their designation, the four commissioners shall select the fifth member, who shall serve as chairman of the commission. If the four members fail to select the fifth member within the time prescribed, a majority of the supreme court shall select him.

(3) Within 90 days after the official final decennial census figures are available, the commission shall file its final plan for congressional districts with the secretary of state and it shall become law.

(4) The commission shall submit its plan for legislative districts to the legislature at the first regular session after its appointment or after the census figures are available. Within 30 days after submission, the legislature shall return the plan to the commission with its recommendations. Within 30 days thereafter, the commission shall file its final plan for legislative districts with the secretary of state and it shall become law.

(5) Upon filing both plans, the commission is then dissolved.