Lassen Peak reaches an elevation of , according to 1992 data from the U.S. National Geodetic Survey; 1981 data from the Geographic Names Information System lists the mountain's elevation at . Lassen Peak marks the southernmost major volcano in the Cascade Range, rising above the northern Sacramento Valley. Bounded by the Sacramento Valley and the Klamath Mountains to the west and the Sierra Nevada mountain range to the south, it is the second tallest peak in the California segment of the Cascades, behind Mount Shasta, which lies to the north. Due to its proximity to nearby volcanoes Mount Tehama and Mount Diller, it is not easy to distinguish from its neighboring peaks.