Dunsmuir is a city in Siskiyou County, northern California. It is on the upper Sacramento River in the Trinity Mountains.
The official city slogan is "Home of the best water on Earth". Dunsmuir is currently a hub for tourism in Northern California, with Interstate 5 in California passing through it. Visitors enjoy fishing, skiing, climbing, or sight-seeing. During the steam locomotive railroad era, it was notable for being the site of an important Central Pacific (and later Southern Pacific) railroad yard, where extra steam locomotives were added to assist trains on the grade to the north.