Starting at the Trespass Creek Trail/Cottonwood Lake trailhead, run up Trespass Creek. Along this wide open basin enjoy the unique geology, flora, and fauna of the Crazy Mountain Range which sits stoically at the far Eastern Front of the Rocky Mountains and takes the brunt of the brutal winds from the expansive plains to the East.
From the head of Trespass Creek drop down the Middle Fork of Sweetgrass Creek toward the popular Campfire Lake. Here many camping options exist as well as fishing and day trip exploration potential.
Next up is to follow the Sweet Grass Trail a bit further before heading up the South Fork of Sweetgrass Creek. A rocky, gorge with waterfalls is sided by wide open mountain meadows. Peaks tower to the left and right of you. At this headwaters find Glacier Lake and an optional side trip that takes you to the top of Conical Peak. Or, if that's not your fancy simply proceed off-trail on a low-class scramble to the col formed between Sweetgrass and Cottonwood Creeks.
From this col descend toward Cottonwood Lake alongside Grasshopper Glacier where you'll find more excellent camping or the option to continue on making your way back to your vehicle at the bottom of Cottonwood Creek. This section of trail is somewhat popular with runners so you'll be sharing the trail but in true SW Montana fashion a friendly wave and a "so, how was the fishing?" will go a long way.
History & Background
The article I am editing said, under description, that you go up the North Fork of Sweet Grass Creek to get toward Glacier Lake. It is the South Fork. Also, in the same paragraph, it mentioned "cool" when it meant "col " I made these corrections