You can find more about Welcome Creek at the U.S. Forest Service Welcome Creek Wilderness page. The wilderness is in the Lolo National Forest and takes up more than 28,000 acres in a 9x7 mile area. There’s pine, fir, and larch trees mostly. The area butts up against the Sapphire Mountains.
Wikipedia has some good info on the place, including its history as a gold mining area. It all started in 1888 when the first discoveries were made, and soon dozens if not hundreds of miners were in the area. Cabins sprouted up along Rock, Welcome, Cinnabar, Chino, Carron, Ferret, and Spartan Creeks, all the way up to the 7,737-foot Cleveland Mountain that dominates the area.
Anyways, it was a fun time, and it’d be a good spot to camp around. If you haven’t been up to Rock Creek and taken the exit, you might want to think about it. Just turn right from Missoula and head 14 miles up the road.
If you go 5 miles up the trail you’ll reach the Cinnabar Cabin, right before Cinnabar Creek. You’ll find some images of the cabin interior in this 2007 Cinnabar Cabin post. The Missoula Independent has a good image of Cinnabar Cabin here. You’ll also find some great Welcome Creek winter images in this 2014 post.
If you want more info on awesome day hikes around Missoula, I highly recommend Day Hikes Around Missoula Montana, a 208-page guide with 83 hikes and maps on every page. Have fun!