Again this year, entry to the three roads below in the Glacier National Park will be by advance reservation only. The booking window will open 120 days before the date of the visit and must be booked the second it opens. Those who reserved an activity within the park (as well as accommodation – hotels and/or overnight parking lots) will not need to order an entry permit to the road from which this activity departs. Those who plan to travel by shuttle on Going to the Sun Road will not need an entry permit either. Those who plan to enter Going to the Sun Road from the east (from Saint Mary) will not need an entry permit this year, as will those who plan to visit the Two Medicine area of the park.
see more info here: https://www.nps.gov/glac/planyourvisit/vehicle-reservations.htm
to reserve: https://www.recreation.gov/timed-entry/10087086
