At the turn of the 20th century, Southern California was a major producer of citrus, the region's primary agricultural export. The industry developed from the country's first navel orange trees, planted in Riverside in 1873. Lobbied by the citrus industry, the UC Regents established the UC Citrus Experiment Station (CES) on February 14, 1907, on of land on the east slope of Mount Rubidoux in Riverside. The station conducted experiments in fertilization, irrigation and crop improvement. In 1917, the station was moved to a larger site, near Box Springs Mountain.