Within the United States, the State of California ranks first in recorded earthquake frequencies. Annually, thousands of shocks are registered on seismometers and many hundreds are actually noticed directly by Californians. In modern times, about one quake per year, destructive to property, has occurred, yet the very large and disastrous events approaching magnitude 8 and higher on the Richter scale are spaced a few decades apart: 1857 in Southern California centered on Tejon Pass, 1872 in the Owens Valley, and 1906 in San Francisco. Unfortunately, the historical record for earthquakes is short in California when compared with accounts for Europe or China, both of which list quakes over a time period of some 2000 to 3000 years. In California, the first historically noted event dates to barely 200 years ago, when in 1769, members of an expedition of the Spanish explorer Gaspar de Portola were knocked to the ground along the Santa Ana River during a large earthquake.