Alaska to California
"Mountain hemlock stands provide good hiding and thermal cover for many wildlife species. Sites dominated by mountain hemlock provide important summer range for deer in Alaska and Vancouver Island because of abundant nutrient-rich forbs available in the understory. In Montana, mountain hemlock habitat types provide summer range for mule deer, elk, and bear. Mountain hemlock seeds have been found in the stomachs of crows and grouse.
Mountain hemlock is important for watershed protection. The mountain hemlock/blueberry (Vaccinium spp.)-copperbush (Cladothamnus pyrolaeflorus)/deer cabbage (Fauria crista-galli) association in Alaska captures runoff from snowmelt." 
"Mountain hemlock is often used as an ornamental for landscaping in the Pacific Northwest and throughout Great Britain. Its dense, compact foliage coupled with its slow growth make it ideal as a garden evergreen. Hemlock species (Tsuga spp.) played a supernatural role as magical objects in the mythology of the Thompson and Lillooet Interior Salish of British Columbia." 
"Mountain hemlock is largely inaccessible because of the high altitudes at which it occurs and is unimportant as commercial timber. It is, however, harvested to a limited extent near its lower limits; the wood is generally marketed with western hemlock. The wood is moderately strong and light colored and is most often used for small-dimension lumber and pulp. The wood is also used for railway ties, mine timbers, interior finish, crates, kitchen cabinets, and flooring and ceilings. Nearly pure stands of mountain hemlock on Prince of Wales Island have been logged for pulp." 
 Tesky, Julie L. 1992. Tsuga mertensiana. In: Fire Effects Information System,. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: https://www.fs.fed.us/database/feis/plants/tree/tsumer/all.html.