There are 45 routes assigned to the "J" zone of the California Route Marker Program, which designates county routes in California. The "J" zone includes county highways in Alameda, Calaveras, Contra Costa, Fresno, Kern, Inyo, Mariposa, Merced, Sacramento, San Benito, San Joaquin, Stanislaus, and Tulare counties.

Inyo County is a county in the eastern central part of the U.S. state of California, located between the Sierra Nevada and the state of Nevada. In the 2020 census, the population was 19,016. The county seat is Independence. Inyo County is on the east side of the Sierra Nevada and southeast of Yosemite National Park in Central California. It contains the Owens River Valley; it is flanked to the west by the Sierra Nevada and to the east by the White Mountains and the Inyo Mountains. With an area of 10,192 square miles (26,400 km2), Inyo is the second-largest county by area in California, after San Bernardino County. Almost one-half of that area is within Death Valley National Park. However, with a population density of 1.8 people per square mile, it also has the second-lowest population density in California, after Alpine County.