Depends on how much distance you want to drive. I94 to I90 straight through to I15 and then North is the best highway to get there. It does take you a little further South than you need to go but you end up with 4 lane all the way. If you want to save on fuel prices, stay south as long as possible. We are definitely higher price right now for gas and diesel.
I can tell you there's not a whole lot to see from Winnipeg to Calgary on the TransCanada Highway (#1) - it is mainly prairie, but it is 4 lane all the way. Although as you drive through the prairie and then head into the foothills and finally to the mountains the scenery just keeps getting better and better. You may want to do what we do - head one way there and one way back. That way you get to see different things.
Head up to Winnipeg, Manitoba, or Regina, Saskatchewan from the USA and then go West on Highway 1 on the way there. Then head back going south from Calgary through Lethbridge and into Montana on I15 and then cross back on I90/I94.
Other alternative is to head West on I94 and take highway 2 or 200 through North Dakota and Montana across to I15 then North and then return down I15 to I90/I94
through Butte, Montana. Or stay on I90 and go right through Rapid City, SD and see the BlackHills. It depends on how much time you have.
You will absolutely enjoy the Banff and Lake Louise Area in the Rockies. Beautiful place.
One additional tip - by staying away from SouthEast Saskatchewan and North East Montana and Northern North Dakota (Williston and Minot) you will avoid the Bakken Fields oil play which is pretty much using up all the campground sites with long term parking right now. Best to head North to Winnipeg or Regina if you go that route as you are then North of all the action.
Also, if you haven't booked for the full service sites yet inside Banff National Park, you may have difficulty getting anything but electric. They book up early. There are some nice places outside the park but we try to get full service inside when we go - usually book when the booking opens up in the spring. I just got 3 out of the 4 days I wanted in Jasper two weeks ago when I booked because we hit middle of the week in August - couldn't get a Friday or Saturday already.
2013 CrossRoads Cruiser Patriot CF345RF
2011 Ford F350 Lariat FX4 CC 6.7L Turbo Diesel (Heavily Modified)