Editing Ventura County, California (section)

===American period===
The [[Mexican–American War]] began in 1846 but its effect was not felt in Ventura County until 1847. In January of that year, Captain [[John C. Frémont]] led the California Battalion into San Buenaventura to find that the Europeans had fled, leaving only Native Americans in the Mission. Fremont and the Battalion continued south to sign the [[Treaty of Cahuenga]] with General [[Andrés Pico]]. The [[Treaty of Guadalupe Hidalgo]] formally transferred California to the United States in 1848.<ref>Murphy, ''A Comprehensive Story of Ventura County, California,'' pp. 12–13.</ref>

By 1849, a constitution had been adopted for the California territory. The new Legislature met and divided the pending state into 27 counties. At the time, the area that would become Ventura County was the southern part of [[Santa Barbara County, California|Santa Barbara County]].<ref>Murphy, ''A Comprehensive Story of Ventura County, California,'' p. 15.</ref>

The 1860s brought many changes to the area. A drought caused many of the ranchos to experience financial difficulties and most were divided, sub-divided and sold. Large sections of land were bought by eastern capitalists based on favorable reports of petroleum deposits. A United States Post Office was opened at Mission San Buenaventura in 1861. On April 1, 1866, the town of San Buenaventura was incorporated, becoming the first officially recognized town in what would become Ventura County.<ref>Murphy, ''A Comprehensive Story of Ventura County, California,'' pp. 16–17.</ref>

On January 1, 1873, Ventura County was officially split from Santa Barbara County, bringing a flurry of change. That same year, a courthouse and wharf were built in San Buenaventura. A bank was opened and the first public library was created. The school system grew, with the first high school opening in 1890.<ref>Murphy, ''A Comprehensive Story of Ventura County, California,'' pp. 22–23.</ref>

Other towns were being established in the county. A plan for [[Port Hueneme, California|Hueneme]] (later Port Hueneme) was recorded in 1874, and [[Santa Paula, California|Santa Paula]]'s plan was recorded in 1875. Along the banks of the Santa Clara River, the township of New Jerusalem (which would eventually be named [[El Rio, California|El Rio]])  was founded in 1875 by the owner of general store named Simon Cohen who became its first postmaster and banker in 1882.<ref>{{Citation |title=El Rio, California |date=July 10, 2023 |url=https://en.wikipedia.org/w/index.php?title=El_Rio,_California&oldid=1164628275 |work=Wikipedia |access-date=October 25, 2023 |language=en}}</ref> The community of Nordhoff (later renamed [[Ojai, California|Ojai]]) was started in 1874.<ref>Murphy, ''A Comprehensive Story of Ventura County, California,'' pp. 23–24.</ref> [[Bardsdale, California|Bardsdale]], [[Fillmore, California|Fillmore]], [[Piru, California|Piru]], and [[Montalvo, Ventura, California|Montalvo]] were established in 1887.<ref>Murphy, ''A Comprehensive Story of Ventura County, California,'' pp. 25–27.</ref>   1892 saw [[Simi Valley, California|Simi]] (later Simi Valley), [[Somis, California|Somis]], [[Saticoy, California|Saticoy]], and [[Moorpark, California|Moorpark]]. Oxnard was a latecomer, not being established until 1898.<ref>Murphy, ''A Comprehensive Story of Ventura County, California,'' p. 27.</ref>

The [[Southern Pacific Railroad]] laid tracks through San Buenaventura in 1887. For convenience in printing their timetables, Southern Pacific shortened San Buenaventura to Ventura. The Post Office soon followed suit. While the city remains officially known as San Buenaventura, it is more commonly referred to as Ventura.<ref>Murphy, ''A Comprehensive Story of Ventura County, California,'' p. 25.</ref> The rail line to [[Northern California]] originally went through [[Saugus, Santa Clarita, California|Saugus]], Fillmore and Santa Paula, providing a boom to those communities along the line. In 1905, Tunnel #26 was completed between [[Chatsworth, Los Angeles|Chatsworth]] and [[Corriganville]] near Simi Valley, shortening the rail route. At a length of {{convert|7369|ft}}, Tunnel #26 was the longest tunnel ever constructed in its day.<ref>{{cite web |url=http://www.chatsworthhistory.com/Documents/PastPresent/Train%20Tunnels%20-%20Ann%20CHS.pdf |title=Chatsworth past & present |last=Vincent |first=Ann |access-date=September 20, 2013 |url-status=dead |archive-url=https://web.archive.org/web/20130921054055/http://www.chatsworthhistory.com/Documents/PastPresent/Train%20Tunnels%20-%20Ann%20CHS.pdf |archive-date=September 21, 2013  }}</ref> This tunnel joined to the railroad spur coming the other direction from [[East Ventura (Metrolink station)|Montalvo]] through Camarillo, Moorpark and Simi Valley, making the [[Coast Line (UP)|contemporary main line]] used today. One stop along the way, at a 90-degree turn, was at a [[sugar beet]] processing factory. The factory bore the name of its absentee owners, the Oxnard Brothers. A small community of farm and factory workers grew near the train stop. That community, now bearing the name of the factory shortened to the one word train stop Oxnard, has become the largest city in Ventura County.<ref>{{cite web|url=https://www.oxnardpd.org/bureaus/departmenthistory.asp |title=History of Oxnard & The Oxnard Police Department |url-status=dead |archive-url=https://web.archive.org/web/20160305043224/https://www.oxnardpd.org/bureaus/departmenthistory.asp |archive-date=March 5, 2016}}</ref><ref>{{cite web|url=http://www.visitoxnard.com/about-oxnard/history-of-oxnard/|title=About Oxnard California - City of Oxnard Information - Visit Oxnard|access-date=May 26, 2017|archive-date=September 21, 2013|archive-url=https://web.archive.org/web/20130921054556/http://www.visitoxnard.com/about-oxnard/history-of-oxnard/|url-status=dead}}</ref>

[[File:SantaBarbaraVenturaOilGasFields.png|thumb|300px|Map of Ventura oil and gas fields]]
Oil has been known in Ventura County since before the arrival of the Europeans, as the native Chumash people used tar from natural seeps as a sealant and waterproofing for baskets and canoes. In the 1860s, several attempts were made to harvest the petroleum products under Ventura County but none were financially successful, and the oil speculators eventually changed from oil to land development. In 1913, oil exploration began in earnest, with Ralph Lloyd obtaining the financial support of veteran oil man Joseph B. Dabney. Their first well, named "Lloyd No. 1", was started on January 20, 1914. The well struck oil at {{convert|2558|ft|m}} but was destroyed when it went wild. Other wells met a similar fate, until 1916, when a deal was struck with the [[Shell Oil Company]]. 1916 was the year that the large [[South Mountain Oil Field]] was discovered; other deals followed with [[General Petroleum]] in 1917 and [[Associated Oil Company]] in 1920. At its peak, the largest oil field in the county, the [[Ventura Oil Field|Ventura Avenue oilfield]], discovered in 1919 in the hills north of Ventura, was producing {{convert|90000|oilbbl}} of oil a day, with annual production of over 1.5{{Nbsp}}million barrels. More oil fields came online in the 1920s and 1930s, with the [[Rincon Oil Field|Rincon field]], the second largest, in 1927, and the adjacent [[San Miguelito Oil Field|San Miguelito]] in 1931.<ref>Murphy, ''A Comprehensive Story of Ventura County, California,'' pp. 27–29.</ref><ref>''California Oil and Gas Fields, Volumes I, II and III''. Vol. I (1998), Vol. II (1992), Vol. III (1982). California Department of Conservation, Division of Oil, Gas, and Geothermal Resources (DOGGR), p. 573.</ref>

In the early hours of the morning of March 12–13, 1928, the [[St. Francis Dam]] collapsed, sending nearly {{convert|12500|e6USgal|abbr=off|sp=us}} of water rushing through the Santa Clarita Valley killing as many as 600 people,<ref>{{cite journal|last=Pollack|first=Alan|url=http://www.scvhs.org/news/dispatch36-2.pdf|title=President's Message|journal=The Heritage Junction Dispatch|publisher=Santa Clara Valley Historical Society|date=March–April 2010}}</ref> destroying 1,240 homes and flooding {{convert|7900|acre|km2}} of land, devastating farm fields and orchards.<ref>Murphy, ''A Comprehensive Story of Ventura County, California,'' p. 31.</ref> This was the single largest disaster to strike Ventura County and the second largest, in terms of lives lost, in the state.