The town was founded in and named New Jerusalem by the owner of general store who became the first postmaster in Located near where the coastal railroad line crosses the Santa Clara River, the town's name was changed to El Rio around The former wagon river crossing route became the Ventura Freeway which separates the community from the commercial developments that grew up on the southwest side of the freeway. That portion of the historic community and sections closer to the river have been annexed to the city of Oxnard.
Vineyard Avenue State Route is the central business district for the largely residential community. The population was 7, at the census, up from 6, at the time the census was enumerated. 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.
Early inhabitants of the area were the Chumash , a Native American tribe who continue to inhabit the area. One of their largest settlements was at nearby Saticoy , because of the bubbling springs that were found there. On May 6, , Juan M. Sanchez β , a former Santa Barbara Presidio soldier, was granted the Rancho Santa Clara del Norte , [ 8 ] which contained 13, acres 57 km 2 of land extending from the Santa Clara River south to the northern boundary of present-day Camarillo , and from the present day Freeway east to the west end of South Mountain.
The town was founded in and named New Jerusalem, California, by Simon Cohn β , [ 10 ] a Prussian Jewish merchant who built a general store at the location. The first one-room schoolhouse was opened in Octaviano and Rosaria Moraga were early settlers who first came to county in the s from Sonora, Mexico. Octaviano worked as the barkeeper at the New Parian Hotel in Ventura , and ran a boarding house they owned in Ventura.
They eventually were able to buy land in New Jerusalem where Octaviano ran a livery stable. He also drove a two-horse stage between Port Hueneme and the Montalvo train station. His descendants were part of the El Rio community up into the 21st century. On February 14, , the postal authority changed the name of the town to Jerusalem. It was reestablished in The post office was discontinued again in East and southeast of town, within the adjoining agricultural area, is the Santa Clara Avenue Oil Field.
