Altadena is an unincorporated area and census-designated place in Los Angeles County, California, United States, approximately 14 miles (23 km) from the downtown Los Angeles Civic Center, and directly north of the city of Pasadena, California. The population was 42,777 at the 2010 census, up from 42,610 at the 2000 census.
Benjamin Eaton first developed water sources from the Arroyo Seco and Eaton Canyon from the mid-1860s from his vineyard near the edge of Eaton Canyon. This made development of Altadena, Pasadena, and South Pasadena possible. He did the work for B.D. Wilson and Dr. John Griffin, who jointly owned the Mexican land grant of the Rancho San Pascual, about 14,000 acres (57 km2) that comprised the future sites of the three communities. They hoped to develop and sell part of this in a real estate scheme called the San Pasqual Plantation. It failed by 1870 despite the irrigation ditch Eaton engineered for the partners that drew water from around the site of present day Jet Propulsion Laboratory in the Arroyo Seco. The failure had two main causes: few believed citrus or other crops could thrive so close to the mountains, and the land was relatively inaccessible.
Eaton then tried to sell the land for the partners, and in late 1873 helped broker a deal with Daniel Berry, who represented a group of investors from Indiana to purchase 4,000 acres (16 km2) of the rancho. Although this included the land of present day Altadena, they developed the 2,500 acres (10 km2) section further south into Pasadena. In 1881, the land that became Altadena was sold to the Woodbury brothers, John and Fred, who launched the subdivision of Altadena in 1887 just as Southern California's great land boom busted. The land remained mostly agricultural. However, several millionaires (mainly from Chicago) built mansions along Mariposa Street, and a small community slowly developed through the 1890s and into the new century.