We will be driving to Glacier Nat. Park after visiting Yellowstone. Our last night will be in Mammoth Hot Springs. My question is ... what is the best route to take? We have accommodations in East Glacier. I have heard so much about Beartooth Hqy that I am wondering if I could go to Glacier via Beartooth and how much extra time I would need. Thanks for any help.

Taking the Beartooth will add about 3 to 4 hours. It is a darn long drive anyway you slice it to East Glacier. If I were to do it, I would leave Red Lodge on state route 78 to I 90.
At Big Timber take US 191 north to State Route 3 and follow it to Great Falls.
Pick up I 15 at Great Falls and follow it north to just north of Conrad. Turn west on route 44 to the US 89 and follow US 89 to Browning. Turn west on US 2 to East Glacier town.

You will be looking at a long day, about 600 miles. But those Montana roads are not that bad and the speed limit is 70 mph. If you are a good driver, you can flat move because nobody drives the speed limit if their vehicle will go that fast! It is a little disconcerting to be doing 75 and have some cowpoke in a beatup pickup roar around you like you were tied to a fence post.
Just be alert for two right angle bends were property lines shifted or the surveyers missed meeting head on!.
Quick 50 yard correction!
90 degrees left and go 50 yards and 90 degrees right. Back on course.

Usually on US routes there is not that problem, and there are none that I recall on route 3. It is the main road to Great Falls and the last time I drove it, I stuck my foot in the carbureter and hauled it. (or should I say fuel injectors)
My only caveat is that you need good 2 lane road passing skills. If you are the type who sticks his grill against the other guys bumper and tries to pass using acceleration, you better be driving a Ferrari. Otherwise if you are good at it, it is sort of fun. I just did a lot downshifting and had my speed way up before I pulled out to pass.
The route is a little hilly, and a slow vehicle can be a challenge if your passing skills are rusty.

If you stay on I 90 all the way to I 15, you drive a heck of a lot farther and our 600 plus miles balloons to 700 plus.

PS If you decide not to, go north from Mammoth to Livingston.
Then you have a choice. Take US 89 to Great Falls with some wiggling throughb the Little Belt Mountains.
Or turn west on I 90, cutoff at route 69 to save many miles,s pick up I 15 south of Great Falls. Contine on I 15 allthe way to route 44 near Conrad and turn west to Vallier and US 89 and on to Browning and US 2 to East Glacier town itself.
It is about the same time wise.
I think I could make it quicker via US 89 in my 6 cylinder Camry which moves on out. You do need a big engine for passing on those roads. Otherwise,if you want serenity of driving take the Interstate. It is quite a bit longer if you stick to the Interstate.
like 210 versus about 150 from livingston. figuring you will average about 70 in the interstate, you will need 3 hours from Livingston. On the regular road you will average about 60, and take about 2.5 hours or less.

Your pick.
I would not take 287 as a cutoff to helena from near Bozeman. Not the best road for speed. I tried it once, and have not used it since, preferring to use route 69 to cut over from I 90 to 15. But I am usually coming or going to West Yellowstone when I do that rather than Mammoth.
Therefore US 89 is not a bargain for me.

Just remember from Mammoth to I 90 north of REd Lodge, you will drive about 165 to 170 miles to get there. And then have about 400 on to East Glacier.
In my younger days, I did not hesitate. At 71 I am a little more conserevative. At 41, 650 in Montana was a normal day's drive.

In Montana,
We sometimes drive 75 miles for lunch!!!

Thanks for the advice on traveling from Red Lodge to Helena. Which routes would you travel from Helena to Many Glacier? Is Route 89 from Great Falls to Browning a two lane road with passing lanes or are we better off on I 15 to Shelby as I prefer driving on interstates? Where would you spend the night? We have reservations for the next night at Many Glacier.

heyjude, where will you be staying in East Glacier? I only found four places to stayover but haven't researched them yet.

Thanks

One of my favorite vacation memories is a driving through Glacier NP with snow falling...on July 4th!

GRACIEB
Come on back out. We had 6 inches of snow yesterday. Sun highway re opened this afternoon.

My brother owns a vacation home with GNP as his backyard. I want to take him up on his offer to stay there, but the airplane tickets are so pricey! Any suggestions?

That trip was the Bicentennial of the Statue of Liberty (?) Does that make sense? Sometime in the early 80's. We were trying to watch the festivities in the NYC waterfront on a tiny portable TV. I don't know which had more snow - the TV or the windshield?!?!?

From Helena,
I would stick with the Interstate to the turn off at exit 348 to Valier.
It is a straight road.
You would join US 89 west of Valier.
There is no need to go to Shelby and Cut Bank. That road US 2, is often crowded by people pulling trailers.

You could take US 287 north to Choteau and then takd US 89 to Browing and the park entrances. US 287 is a little shorter, but I think your average speed on I 15 would be greater and with easier driving.

The speed limit on I15 drops in some places because the road is curvey over the mountains. But mostly it is 75 mph.
And people drive 80 and more.

I was coming south from Great Falls doing about 80, and a black car, probably a BMW 500 series, went by me so fast I was not sure what it was. My wife leaned over, looked at the speedometer, and said, "Well, I thought for a moment you had stopped."