At the time of the Japanese attack on Pearl Harbor on December 7, 1941, the West Coast of the United States already had a long tradition of anti-Chinese and anti-Japanese discrimination. The Japanese came later than the Chinese. In 1890 there were only 3,000 Japanese people in the whole United States. When Hawaii became a United States Territory in 1898, the Japanese there were free to move to the mainland. In 1900, over 12,000 arrived, mostly from Hawaii. Between 1900 and 1908, 135,000 Japanese individuals entered the country, most settling on the West Coast, especially in California. Politicians, labor leaders, and newspaper publishers campaigned to restrict further immigration into the state. Reacting to this pressure, the United States and Japan agreed in 1908 to reduce immigration ("The Gentlemen's Agreement"). In 1924, the United States prohibited Japanese immigration entirely. Immigrants already in this country (Issei, from the Japanese word for "one") were barred from citizenship, but their children (Nisei, from the word for "two"), born in the United States, were automatically citizens.

Over the years, the Japanese population in America prospered, and by the outbreak of World War II, many Japanese had left the ranks of low-paid workers to become owners or managers of farms, fishermen who owned their own boats, and operators of small stores and other businesses. Their very success brought complaints against them from agricultural interests who wanted to eliminate competition. When World War II began in the Pacific with Japan's devastating attack on Pearl Harbor, fear of an attack on the West Coast created even greater antagonism toward Japanese immigrants and their children. In 1942, fear and prejudice combined to confine nearly 120,000 people of Japanese ancestry, citizens and aliens alike, in relocation centers established by the U.S. government in remote areas west of the Mississippi River. Many would not pass through the barbed wire fences surrounding the centers until the war was over.