Westwood is a census-designated place (CDP) in Lassen County, California, United States. Westwood is located 20 miles (32 km) west-southwest of Susanville, at an elevation of 5,128 feet (1,563 m). The population was 1,647 at the 2010 census, down from 1,998 at the 2000 census.
Westwood is built upon lava flows from Cascade Mountain Range volcanoes to the north. Keddie Ridge is considered to be at the northern end of the Sierra Nevada Mountain Range.
According to the United States Census Bureau, the CDP has a total area of 5.5 square miles (14 km2), of which 5.4 square miles (14 km2) is land and 0.1 square miles (0.26 km2) (1.34%) is water.
Westwood was built by T. B. Walker to be the operations center for the Red River Lumber Company in 1913, and serviced by the Fernley and Lassen Railway built in 1912-14. The first post office opened in 1913. The Red River Lumber Company is credited as being "the world's largest electrical sawmill of the times." Red River Lumber Company also operated one of the first electric railways in the state built in 1927. The mill was equipped with the most modern equipment for its time; and the surrounding territory was crisscrossed by forest railways bringing logs to the mill. The railway shop at Westwood was home to 2-8-0 #102 and 2-8-2 #104 when forest railway operations ceased in the early 1950s.