The geographic range of Tsuga mertensiana fairly closely matches that of Tsuga heterophylla (western hemlock), likewise mostly less than from the Pacific Ocean apart from a similar inland population in the Rocky Mountains in southeast British Columbia, northern Idaho and western Montana. The inland populations most likely established after deglaciation by remarkable long-distance dispersal of more than 200 km from the coast populations. Their ranges, however, differ in California, where western hemlock is restricted to the Coast Ranges and mountain hemlock is found in the Klamath Mountains and Sierra Nevada. Unlike western hemlock, mountain hemlock mostly grows at high altitudes except in the far north, from sea level to in Alaska, in the Cascades in Oregon, and in the Sierra Nevada.