This digital publication contains all the geologic map information used to publish U.S. Geological Survey Scientific Investigations Map SIM 2899 and additional photographs. The geologic map of Lassen Volcanic National Park (LVNP) and vicinity encompasses 1,905 km² at the south end of the Cascade Range in Shasta, Lassen, Tehama, and Plumas Counties, northeastern California. Most of the map area is underlain by middle to late Pleistocene volcanic rocks; Holocene, early Pleistocene, and late Pliocene volcanic rocks (<3.5 m.y.) are less common. The southernmost Cascade Range consists of a regional platform of basalt and basaltic andesite, with subordinate andesite and sparse dacite, erupted from small, relatively short-lived volcanoes. Nested within these regional volcanoes are "volcanic centers," defined as large, long-lived, composite, calc-alkaline edifices erupting the full range of compositions from basalt to rhyolite but dominated by andesite and dacite. Volcanic centers are produced by the focusing of basaltic flux from the mantle and resultant enhanced interaction of mafic magma with the crust. Collectively, volcanic centers mark the axis of the southernmost Cascade Range. The map area includes the entire, presently active, Lassen Volcanic Center, parts of three older volcanic centers (Maidu, Dittmar, and Latour), and the products of regional volcanism. The deposits of several glacial advances are widespread.