El Rio (/ɛl ˈriːoʊ/ ⓘ; Spanish: El Río, meaning "The River") is a small, rural[6] unincorporated town in Ventura County, California, United States, on the northeast side of the 101 Freeway and Oxnard, and south of the Santa Clara River.

Located near where the coastal railroad line crosses the Santa Clara River, the town's name was changed to El Rio around 1900.

That portion of the historic community and sections closer to the river have been annexed to the city of Oxnard.

Vineyard Avenue (State Route 232) is the central business district for the largely residential community.

For statistical purposes, the United States Census Bureau has defined a portion of the unincorporated area as El Rio census-designated place (CDP) which does not precisely correspond to the historical community that is much larger with significant portions having been annexed to the city of Oxnard.

The post office later changed its name to El Rio in 1895, which is the Spanish translation for “the river”.

[7]: 4.12-1  The Chumash region extends from Point Conception to Santa Monica and back into the foothills as far as the Coast Range.

On May 6, 1837, Juan M. Sanchez (1791–1873), a former Santa Barbara Presidio soldier, was granted the Rancho Santa Clara del Norte,[8] which contained 13,989 acres (57 km2) of land extending from the Santa Clara River south to the northern boundary of present-day Camarillo, and from the present day 101 Freeway east to the west end of South Mountain.

[9] Sanchez and his wife, Ines Guevara de Sanchez (1794–1862), had their adobe home built below the western slope of South Mountain, within a heavy group of eucalyptus trees at the east end of present-day Rose Avenue, an avenue that was lined on both sides with tall eucalyptus trees.

The town was founded in 1875 and named New Jerusalem, California, by Simon Cohn (1852–1936),[10] a Prussian Jewish merchant who built a general store at the location.

[13] It was the first Catholic church to be built in Ventura County since the founding of Mission San Buenaventura 95 years earlier.

[20] According to the United States Census Bureau, the census-designated place (CDP) has a total area of 2.0 square miles (5.2 km2), all of it land.

East and southeast of town, within the adjoining agricultural area, is the Santa Clara Avenue Oil Field.

There were 1,700 housing units at an average density of 840.0 per square mile (324.3/km2), of which 981 (60.2%) were owner-occupied, and 648 (39.8%) were occupied by renters.

[25] Poet and novelist Michele Serros a book-signing event here in 2006 when her young-adult novel “Honey Blonde Chica” was published.

[32][31] The area storm water drains into the adjacent Santa Clara River.