Montana has several different residency requirements.
Driver’s Licenses – For the purposes of obtaining a Driver’s License, you are considered a Montana resident after living in the state for 60 consecutive days, and must have a Montana license in order to operate a motor vehicle. For commercial drivers, the requirement is 30 days.
Hunting/Fishing – For hunting and fishing licenses, you are considered a Montana resident after 180 days. After residency is established, you must continue to live in Montana at least 120 days a year and meet a number of other residency criteria.
State Colleges & Universities – For the purposes of higher education, a student must reside in Montana for a minimum of one full year prior to registration.