Mont. Code Ann. § 35-20-102

The presiding officer and secretary of the meeting described in 35-20-101 shall immediately after the election divide the trustees by lot into three classes, those in the first class to hold their office for 1 year, those in the second class for 2 years, and those in the third class for 3 years. However, the trustees of each class may be reelected if they possess the qualifications mentioned in this part. The meeting must also determine on what day in each year the future annual election of trustees will be held.