The Mount Diablo meridian is named for the location of its initial point on Mount Diablo in California. The meridian extends to the north and south from Mount Diablo and is used to describe lands in most of northern California. Along this meridian is a fractional township area encompassing land in northern California adjacent to the Oregon-California border, much of which is currently part of the Lower Klamath National Wildlife Refuge. The area is south of Klamath Falls and west of Tulelake, California. The Townships is referred to as fractional due to improper surveying, possibly because of a large body of water located in the area. Lower Klamath Lake is located within the fractional township area and had likely interfered with the survey.