This study examines the socioeconomic advancement of Korean immigrants in California from 1905 to 1920. Based on county archives, special collections, oral histories, U.S. government documents, contemporary studies, and newspapers, this study analyzes how the Korean immigrants in California were influenced by the World War I rice boom and made efforts to develop their status in California at the start of the twentieth century. Successful rice cultivation started in California around 1912 and this new agricultural development provided opportunities for Koreans to make the transition from migratory farm laborers to rice farmers. This study presents the unique adjustment pattern of exceptional Korean immigrants who made significant efforts to adjust to Californian society and improve their socioeconomic status; however, in this process, they continued to strongly express their Korean identity and contributed to Korean independence rather than develop an outward loyalty to the United States. Korean immigrants’ successful adjustment to California resulted from their combined efforts to maintain their Korean identity, overcome racial discrimination that denied them citizenship rights, and promote the upward mobility of ethnic Koreans.