Later known as “Japanese Internment Camps”
However, strangely enough, there is no language in the order itself specifying the Japanese or any other ethnic group. From archives.org:
The West Coast was divided into military zones, and on February 19, 1942, President Franklin D. Roosevelt issued Executive Order 9066 that authorized military commanders to exclude civilians from military areas. Although the language of the order did not specify any ethnic group, Lieutenant General John L. DeWitt of the Western Defense Command proceeded to announce curfews that included only Japanese Americans.
Reading further reveals it was not Roosevelt but DeWitt who turned what was a generic “exclude civilians from military areas” order into an “imprison 122,000 people, 70,000 of them citizens” order.
General DeWitt first encouraged voluntary evacuation by Japanese Americans from a limited number of areas. About seven percent of the total Japanese American population in these areas complied. Then on March 29, 1942, under the authority of Roosevelt's executive order, DeWitt issued Public Proclamation No. 4, which began the forced evacuation and detention of Japanese-American West Coast residents on a 48-hour notice. Only a few days prior to the proclamation, on March 21, Congress had passed Public Law 503, which made violation of Executive Order 9066 a misdemeanor punishable by up to one year in prison and a $5,000 fine.
In the next six months, approximately 122,000 men, women, and children were forcibly moved to "assembly centers." They were then evacuated to and confined in isolated, fenced, and guarded "relocation centers," also known as "internment camps." The 10 sites were in remote areas in six western states and Arkansas: Heart Mountain in Wyoming, Tule Lake and Manzanar in California, Topaz in Utah, Poston and Gila River in Arizona, Granada in Colorado, Minidoka in Idaho, and Jerome and Rowher in Arkansas.
Nearly 70,000 of the evacuees were American citizens. The government made no charges against them, nor could they appeal their incarceration. All lost personal liberties; most lost homes and property as well. Although several Japanese Americans challenged the government’s actions in court cases, the Supreme Court upheld their legality.
Well, that’s pretty much how that’s going to work when, 3 months after Pearl Harbor, you designate the Secretary of War to decide how to enforce such broad new powers. His goal is to run the war, and now you gave him carte blanche to strip rights from citizens. And then he delegates that power to a Lieutenant General in the Western Defense Command.
Was it legal? Not exactly. But Lincoln suspended habeus corpus during the Civil War. That wasn’t “legal”, exactly.
Wartime tends to muddy the waters on what is strictly legal and what is not.
And it’s not like this attack on Japanese ethnics came out of nowhere. California led the way (as a result of the Gold Rush of 1848 and completion of the Trans-Continental railroad in 1869 both of which brought many Chinese into the area) with anti-Chinese sentiment leading to the Chinese Exclusion Act of 1882, a federal law prohibiting any further such immigration for ten years — and was subsequently renewed several times.
Later, California passed the California Alien Land Law of 1913 which prohibited “aliens ineligible for citizenship from owning agricultural land or possessing long term leases of it”, targeting primarily Japanese farmers after an influx of indentured servants from Hawaii in 1900. It was overturned in 1952 by the U.S. Supreme Court as a violation of the equal protection clause of the 14th Amendment.
There was plenty of public support for anti-Asian discrimination, in other words. These examples are just scratching the surface.
A map from the National Park Service site showing the locations and max populations of the camps.