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Sonoma Valley is the birthplace of the California wine industry and often called The Valley of the Moon. Sonoma Valley is home to some of the earliest vineyards and wineries in the state, some of which survived the phylloxera epidemic of the 1870s and the impact of Prohibition. Its wineries are generally well prepared for receiving tourists, and Sonoma Valley offers a wide range of year-round festivals and events, including the prestigious Sonoma International Film Festival. Today, this small valley's wines are protected by the US Federal Government's Sonoma Valley and Carneros AVAs (or American Viticultural Areas).
The valley is located in southeastern Sonoma County between the Mayacamas Mountains and Sonoma Mountains. It stretches from San Pablo Bay in the south to the city of Santa Rosa in the north. Sonoma Creek flows down the valley to the bay. The area includes the incorporated city of Sonoma and part of the City of Santa Rosa, as well as numerous unincorporated communities, including Kenwood and Glen Ellen near Santa Rosa and, near Sonoma, El Verano, Boyes Hot Springs, Fetters Hot Springs, and Agua Caliente.
Once a valley of the coastal Miwok, Pomo and Wintun peoples, called the Valley of the Moon in their legends, the valley was selected by the Franciscan order of Spain as the site to build the Mission San Francisco Solano, the northernmost mission in their chain of twenty-one missions built in Alta California. Established in 1823 and named to honor St. Francis Solanus, Mission Solano was the sole California mission established under the rule of a newly-independent Mexico. Within two generations of the Spaniards' arrival, however, the indigenous societies of the region were dispossessed of their land and decimated by diseases to which Europeans were resistant. Soon after the Sonoma mission was built, it was secularized by the Mexican government, and, under the orders of Lieutenant, later General Mariano Guadalupe Vallejo, el Pueblo de Sonoma (the town of Sonoma) was laid out in the standard form of a Mexican town, centered around the historic plaza, which is still the town's focal point. The raising of the first California Bear Flag and Vallejo's arrest in 1846 by a band of Americans claiming to act on the orders of Col. John C. Fremont was the initial act that founded the Bear Flag Republic. Vallejo later transferred his allegiance with US statehood (1850), and with his amassed land holdings guided the development of the town and dispensed large ranches throughout the valley. California's first wineries were established here, including Buena Vista Winery (1857) and Gundlach Bundschu (1858).
The other communities in the valley, such as Kenwood, Glen Ellen, Schellville, and Boyes Hot Springs, were founded later in the 19th century, some as resorts centered on the geothermic hot springs that still well up from deep within the earth. Boyes Hot Springs and Agua Caliente were popular health retreats for tourists from San Francisco and points beyond until the middle of the 20th century. Today the Sonoma Mission Inn in Boyes Hot Springs remains as a main destination resort, and the wineries, the historic sites, and the area's natural beauty are the main tourist attractions.
Origin of the name 
According to Jack London, who had a ranch there, the Native American word Sonoma means Valley of the Moon. He used it for his book of the same name. But there are several other possible translations for Sonoma (see Sonoma County, California). According to the Miwok tribes that lived in the valley, and the Pomo, it meant "valley of the moon" or "many moons". White settlers may have accidentally translated the words "many moons" into "valley of moons". Miwok legends say that the moon seemingly rose from this valley, or was "nestled" in the valley, or may have even sprung up multiple times in one night.
The Sonoma Valley is part of the Coast Range Physiographic provence. Basement rocks that make up the valley at great depth are the Great Valley Sequence shale, sandstone and conglomerate deposited in a continental slope- to abysmal plain environment via turbidite flows. The Cretaceous Great Valley Sequence overlies and contacts the Franciscan Complex along the Coast Range Thrust. The Jurassic-Cretaceous Franciscan Complex includes crumpled, uplifted terranes that have resulted from the subduction of the former oceanic Farallon Plate under the North American continent. During late Miocene-Pliocene time (~10 to ~4 million years) the area was attended by volcanism (Late Miocene Tolay Volcanics and Late Miocene - Pliocene Sonoma Volcanics) which are interbedded with the late Miocene-Pliocene Petaluma Formation. The (~9 to 4 million year old) Petaluma Formation was a fresh-water river system flowing from east to west and through the volcanics. At that time, volcanic lava flows and river sands and gravels were actively deposited together, hence "interbedded lavas and gravels". The volcanoes may have been similar to island arcs. The Petaluma Formation is found in outcrop from Sears Point to Santa Rosa (through Sonoma Mountain) and as far west as Cotati where it interfingers with a marine sandstone called the Wilson Grove Formation. Gravels in the Petaluma Formation did not come from rocks located in Napa, but have been sourced to mountains east of San Jose, California. This does not mean rivers flowed northward from San Jose to Sonoma; rather, strike-slip movement along the Hayward-Sonoma Valley-Carneros fault system has dislocated present-day Sonoma County north and away from the mountains in San Jose where the basin formed.
The valley is drained by Sonoma Creek, whose headwaters rise in Sugarloaf Mountain State Park and discharge into the San Pablo Bay at the Napa Sonoma Marsh. Some of the principal tributaries to Sonoma Creek are Yulupa Creek, Graham Creek, Calabazas Creek, Bear Creek, Schell Creek and Carriger Creek.
In spring 2006, the United States Geological Survey in conjunction with the Sonoma County Water Agency completed a comprehensive basin-wide groundwater study to characterize groundwater resources in the Sonoma Valley. The report can be obtained on the USGS publications website. Currently, a Basin Advisory Panel, composed of stakeholders from agriculture, environmental groups, domestic well owners, municipalities and government is working to develop a groundwater management plan to protect groundwater resources in the valley.
Points of interest 
- Quarryhill Botanic Garden
- Mission San Francisco Solano
- Jack London State Historic Park
- Sonoma State Historic Park
- Sonoma Creek
- Wine Country
- 'The Sonoma Plaza' (The Town Square) and on the Official National Registry of Historic Sites
- Blue Wing Inn of 1840, where such notable guests, according to local tradition, included John C. Frémont, U. S. Grant, Governor Pío Pico, Kit Carson, Fighting Joe Hooker, William T. Sherman, Phil Sheridan, and members of the Bear Flag Party.
- General Mariano Guadalupe Vallejo Home: Official residence of the last Spanish Governor.
- Presidio of Sonoma adobe:
- Toscano Hotel
- Swiss Hotel - Adobe structure and original home of Vallejo's brother, located on 'The Square' (see link below)
- Sebastiani Theatre - A historical theatre built in 1933 by Samuele Sebastiani as a movie house.
- Sonoma TrainTown Railroad - miniature amusement park
- Depot Park
See also 
- Category:Sonoma County wineries
- Sonoma Valley Film Festival
- Sonoma Raceway
- The Valley of the Moon (novel)
- Hanna, Phil Townsend (1951). The dictionary of California land names. The Automobile Club of Southern California, Los Angeles. p. 311.
- May, James (2003). "Why Graton...?". Indian Country - Legend of Valley of the Moon.
Kroeber, A. L., Handbook of the Indians of California (New York 1976 - reprint of Bulletin 78 of the Bureau of American Ethnology of the Smithsonian Institution 1925)
- Sonoma Valley Visitors Bureau
- Overview of Sonoma County geology
- Sonoma Valley Chamber of Commerce
- Sonoma Valley Film Festival
- Sonoma Valley Wiki
- List of Sonoma Wineries with Free Tastings