Casa de Oro-Mount Helix is a census-designated place (CDP) in the East County region of San Diego County, California. As of the 2020 census, Casa de Oro-Mount Helix had a population of 19,576.
The CDP encompasses several unincorporated neighborhoods near the cities of El Cajon and La Mesa and the CDP of Spring Valley. Locations in the northern (Mount Helix) part of the CDP use La Mesa addresses, while locations in the southern (Casa de Oro) part use Spring Valley addresses. Informally, Casa de Oro is often considered to be a part of Spring Valley.
History
thumb|312x312px|Mount Helix behind the steeple of Santa Sophia Church (inaugurated 1958)
In 1872, after a scientist discovered a European snail (Cornu aspersum, formerly Helix aspersa) living on a small mountain, Rufus King Porter, the founder of what is now unincorporated Spring Valley, California, named the peak Mt. Helix. Then in 1885, the United States Postal Service rejected the use of two words for a post office name, so Rufus submitted just the name Helix and also became the first postmaster in Spring Valley; the Helix Post Office was operated out of his home.
Around this same time, Hubert Howe Bancroft came to the area. He bought the Porters' ranch and also acquired neighboring properties, accumulating about . He began calling his property "Helix Farms." Bancroft hired workers to help develop Helix Farms, planting orchards and building structures for his ranch. By the early 1900s, Helix Farms was home to the largest olive ranch in southern California; some of the original olive trees can still be found today. Bancroft died in 1918, and eventually his family sold the property.
Geography
Casa de Oro-Mount Helix is located at (32.763359, -116.977474).
According to the United States Census Bureau, the CDP has a total area of , all land.