Plan ahead
In General
It’s better to have a car. Relying on ride-shares or public transportation in Montana will not be pleasant (or possible in a lot of cases). Def recommend renting one.
Montana and many of its must-see sights and locations were not built to handle 21st-century crowds. Space is limited and often books out months (if not years) in advance. Planning well ahead is important if you want to make the most of your time.
Cell service and internet can be spotty in Montana (especially in the deeper parts of the National Parks). Download maps, and itineraries before you arrive. It'll save you time and stress.
National Parks
Since the pandemic, both Glacier and Yellowstone National Parks have implemented vehicle registration systems that ask you to purchase your entrance passes before you arrive. Please plan well ahead, as these registrations are often on a first-come-first-serve basis and they do run out. Check the websites to see when they go on sale for the dates you're hoping to visit and book right away when possible.
Glacier National Park Fees & Passes Page
Yellowstone National Park Fees Page
Within both Glacier and Yellowstone National Parks there are incredible, historic lodges that offer accommodations for visitors. They often book out a year in advance but keep checking sites as there are cancellations that open up rooms. If you cannot secure accommodations within the park, try to stay just outside of the parks (St. Mary for Glacier; West Yellowstone for Yellowstone). It's also worth noting that the lodges in the parks are very old and thus have thin walls. Ear plugs might be worthwhile if you're a light sleeper.
Many Glacier Lodge
Lake McDonald Lodge
Anywhere near Old Faithful (multiple options)
Anywhere near Lake Yellowstone (multiple options)
Glacier National Park is huge, mountainous terrain. There is only one road through the park (Going To The Sun Road). One of the best drives in the world.
Always keep an eye out for bears, mountain lions, and moose. Making noise along a hiking trail is the best way to ensure you don't surprise and frighten them. Also strongly recommend buying bear spray when you're here (you can't fly with it).
Wait, there’s more!
These are just our takes on what to do and see. The more time you have the better. It's a big state (4th largest in terms of land mass), so we’re only scratching the surface here. There are plenty of things that would make for a great adventure that aren't on our map of recommendations. Flathead Lake, The Big Sky area, Big Hole Valley, Bozeman and countless fishing opportunities come to mind. Hopefully, this just serves as a solid outline of where to begin.