State Route 89 (SR 89) is a state highway in the U.S. state of California that travels in the north–south direction, serving as a major thoroughfare for many mountain communities in the Sierra Nevada and the Cascade Range. It starts from U.S. Route 395 near Topaz Lake, winding its way up to the 8,314-foot (2,534 m) Monitor Pass, down to the Carson River, and up again over the 7,740-foot (2,359 m) Luther Pass. From that point on, the route generally loses elevation on its way past Lake Tahoe, through Tahoe and Plumas National Forests until Lake Almanor. For roughly nine miles the route is then a part of State Route 36. The route then ascends to the 5,753-foot (1,754 m) Morgan Summit. After it enters Lassen Volcanic National Park it continues to gain elevation until it reaches its highest point in an unnamed pass in the middle of Lassen Peak and Bumpass Mountain. The road then descends and heads northwest, finally terminating at Interstate 5 at the foot of Mount Shasta at around 3,600 feet (1,100 m).
