|Cornelius Boy Jensen|
|Born||September 29, 1814
|Died||December 12, 1886|
|Residence||Agua Mansa, California, U.S.|
|Nationality||Danish, later American|
|Title||Member of the San Bernardino County Board of Supervisors|
|Term||Held nine 1-year terms from 1856 to 1877|
Cornelius Boy Jensen (September 29, 1814 – December 12, 1886) was a Danish sea captain and California politician. Of the nine one-year terms that he served as county supervisor between 1856 and 1877, Jensen was the Chairman of the San Bernardino County Board of Supervisors four times. His Agua Mansa home, the Jensen Alvarado Ranch, is a registered California Historical Landmark (No. 943) and is listed on the National Register of Historic Places.
Jensen was born on the North Frisian island of Sylt off the coast of Southern Schleswig (then part of Denmark, now in Germany) in either 1812 or 1814. He took his mate's exam in Denmark and thereafter made several trips around Cape Horn, arriving in California by 1844.
Jensen was captain of his own vessel for 20 years. He arrived in San Francisco in 1848. With news of the California Gold Rush, his crew jumped ship and he, too, became a "Forty-niner" in search of gold. When that no longer suited him, he went to Sacramento and opened a store, selling items to the gold miners. It was here that he met the Californio Ignacio Alvarado. At Alvarado's urging Jensen moved to Southern California, settling in Agua Mansa around 1854. At the age of 40, he married Alvarado's 16 year old sister, [nb 1] Mercedes Alvarado (c. 1848–1914) at Mission San Gabriel in 1853. Her parents were Francisco and Juana Maria (Avila) Alvarado.
Jensen had several careers after his early years as a sea captain. In addition to being a rancher and vintner on his Southern California properties, he owned a sawmill and a store, and served as a politician.
After the Great Flood of 1862 destroyed much of the town of Agua Mansa, Jensen and his wife built a home on hundreds of acres on what was to become the Cornelius and Mercedes Jensen Ranch, a California Historical Landmark, located at the Jensen-Alvarado Ranch Historic Park and Museum. Their brick home, the oldest non-adobe structure in the Inland Empire, was Riverside County's first kiln-fired brick building.
Of their 12 children, ten survived into adulthood. His oldest son was Jose (born 1855) who made a career as a deputy assessor, judge of elections, and member of the board of education. Henry (born 1867) was a member of the school board. Their son John, who married Emily Crowder, built a wood framed home that was subsequently moved to the Jensen-Alvarado Historic Ranch and Museum, serving as the caretaker's home.
Mercedes' sister, Delores, married Fenton Slaughter who also sat on the San Bernardino County Board of Supervisors. Jensen's cousin, Peter Peters, who also hailed from Sylt, married Mercedes' other sister, Refugio; Peters served on the local school board and was a trustee of the Agua Mansa Pioneer Cemetery.
- Though the reference states that Mercedes was Ignacio's daughter, genealogical records show Ignacio (or Ygnacio) to be her brother.
- Summons, Trevor (2010-08-21). "Ranch offers rich look at past". The Sun (San Bernardino Sun). Retrieved 12 January 2012.
- "Across Oceans, Across Time". dkmuseum.org. Retrieved 12 January 2012. "However, when a descendant visited Sylt, she was told in no uncertain terms by a local historian that her ancestor was Frisian, not Danish. ... His surname Jensen indicates at least some ethnic Danish heritage, while Boy(e) is a common Frisian name."
- "Cornelius Jensen, 1815 – December 12, 1886". oac.cdlib.org. Online Archive of California. Retrieved 10 December 2010.
- Johnson, Kim Jarrell (2006). Jurupa. Arcadia Publishing. p. 18. ISBN 0-7385-3082-4.
- Sheffield, Larry (2004). Colton. Arcadia Publishing. p. 17. ISBN 0-7385-2901-X.
- "Kalifornien – Cornelius Boy Jensen" (in German). Nordfriisk Instituut. Retrieved 10 December 2010.
- "Cornelius Jensen". San Bernardino Public Library. Retrieved 10 December 2010.
- Holmes, Elmer Wallace (1912). History of Riverside County, California: with biographical sketches of the leading men and women of the county who have been identified with its growth and development from the early days to the present. Historic Record Company. p. 485.
- Jaques, Susan (September 15, 1991). "Settling In : Jensen-Alvarado Historic Park Celebrates Early Pioneers Who Changed Southland". Los Angeles Times. Retrieved 10 December 2010.
- "Mercedes Alvarado". Quill Cottage Family Tree. Retrieved 10 December 2010.
- Henderson, Monique R. (January 16, 2010). "Jensen-Alvarado Ranch house gives glimpse of 1800s". The Press-Enterprise. Retrieved 10 December 2010.
- Holmes, p. 486-487
- Holmes, p. 524
- Sheffield, p. 18