area of spirelike rock formations 500 to 1,200 feet (150 to 365 metres) high in the hilly Gabilan Range of west-central California, U.S. The pinnacles lie just west of the San Andreas Fault (the main component of the San Andreas Rift Zone), about 25 miles (40 km) southeast of Salinas. The monument, created in 1908, has an area of 25 square miles (65 square km); another 12 square miles (32 square km) was added by presidential proclamation in 2000, a portion of which subsequently has been acquired.

The pinnacles were formed by volcanic activity about 23 million years ago during the Tertiary Period some 195 miles (315 km) south of their present location. They have moved slowly northwestward by tectonic activity as the Pacific Plate has slid along the edge of the North American Plate; a remnant of the formation still exists in its original location, a short distance northeast of Los Angeles. The monument also has talus caves that can be explored and is popular with hikers and rock climbers. A foot trail leads to the highest point, North Chalone Peak, which reaches 3,304 feet (1,007 metres). The monument's surface is covered by chaparral vegetation; deer, rabbits, foxes, mountain lions, tarantulas, and the Townsend's big-eared bat (Plecotus townsendii) are among the wildlife found there.