2004: 150th Anniversary of the San Francisco Tide Gauge

The San Francisco tide station has measured the rise and fall of tides continuously since June 30, 1854.

On June 30, 1854, the United States Coast Survey, the oldest federal scientific agency, installed a self-recording tide gauge in San Francisco Bay. This station has measured the rise and fall of tides continuously ever since, making it the nation’s oldest continually operating tidal observation station. This location also has the longest continuous tide record in the Western Hemisphere. The gauge even survived the earthquake of 1906.

The San Francisco tide station plays an important role in navigation, ocean science, and climatology today as it has throughout its 150-year history. Besides guiding mariners to safe passage, the station monitors sea level change and tsunamis and helps measure the effects of the El Niño and La Niña global climate phenomena on sea level. Soon after its installation in 1854, the gauge measured tsunami waves generated by an earthquake in Japan. This helped to estimate the average depth of the Pacific Ocean.

The San Francisco tide gauge is housed in this structure near California's Golden Gate Bridge (in background). (Photo: Center for Operational Oceanographic Products and Services, NOAA)

The station is part of the National Water Level Observation Program, which consists of 175 continuously operating water level measurement stations along the U.S. coasts and the Great Lakes regions. The normal tidal range (difference between high and low tide) during a full moon at the San Francisco station is approximately 5.8 feet.