Mount Shasta is a city in Siskiyou County, California, United States, at about 3,600 feet above sea level on the flanks of Mount Shasta, a pr…Mount Shasta is a city in Siskiyou County, California, United States, at about 3,600 feet above sea level on the flanks of Mount Shasta, a prominent northern California landmark. The city is less than 9 miles southwest of the summit of its namesake volcano. Its population is 3,223 as of the 2020 census, down from 3,394 from the 2010 census.