Native Americans were replaced in the late 1800s by Chinese workers brought to Riverside by Chinese labor contractors. By 1885 nearly 80 percent of the labor force was Chinese. The considerable horticultural skills and knowledge that they brought with them made citriculture enormously successful. However, the Chinese Exclusion Act of 1882, as well as a climate of anti-Chinese sentiment, caused their numbers to dwindle.
With fewer Chinese available, Japanese immigrants moved in to fill the need. By 1900 the citrus industry in Riverside alone employed about 3,000 Japanese workers, hired through Japanese labor contractors. Between 1900 and 1920 they were the largest labor group in the citrus industry. However, anti-immigrant sentiment eventually drove them out. Around 1919 Hispanic workers began to arrive, along with other immigrant nationalities. They came with their families and formed communities wherever they worked. Hispanic workers quickly grew to supply 30 percent of the workforce. By the mid-1940s they constituted approximately two-thirds of the citrus industry’s labor force, while women became the mainstay in citrus packing houses.