Location: Los Angeles County, California

Named by USFS surveyor Don McLain (1918). It has long been assumed that it was for Robert Stockton Williamson (1824-82), an officer in the U.S. Army Corps of Topograhical Engineers, who at the direction of Secretary of War Jefferson Davis, made a reconnaissance of the north side of the San Gabriels (1853). This "Pacific Railroad Survey" was to locate a route for a proposed transcontinental railway linking San Francisco with the East Coast by a southerly route along the 32nd parallel.

Survey geologist, William Blake, first noted that the east to west orientation of our local mountains differed from the Sierra, and coined the term Transverse Ranges-this was the only name given by this team that still survives in use. They never penetrated our mountain ranges (which Blake called Bernardino Sierra, and Williamson labeled Qui quai-mungo), although they successfully identified Soledad Canyon as the best railway route through them.

Gudde states that this mountain was named by the Whitney Survey (1864).

In an interview, Don McLain told John Robinson that he had named this peak for Will Williamson, a friend of his. When reminded of Lt. Williamson, McLain added "Well, yes, I named [it] for him too". Angeles N.F. historian Don Hedly reported this same Williamson story from McLains widow.

Name first appears on USFS Angeles National Forest map (1920).

Peak was on the original 1946 HPS Peak List. Weldon Heald climbed this peak in 1942.