The City of Rocks National Reserve features granite spires and monoliths reaching 60 stories tall. Geologists estimate the oldest granite to exceed 2.5 billion years. Established in 1988 as a national reserve, City of Rocks encompasses 14,407 acres of land (about one quarter is privately owned) and is renowned for its scenic, geologic, and historic significance. The City of Rocks area was an important landmark on the California Trail.