Now I am watching this 1940′s propaganda film for the internment camps in which we placed Japanese-Americans. I recommend it, as contains a great deal of information about camp conditions, which are quite gulag-esque despite all attempts at positive spin.
It seems that the modern concentration camp was invented in the 1890′s. Spain had them in Cuba, to prevent civilians from aiding and abetting insurgents, and Great Britain had them in South Africa for Boer and African civilians. These were not intended as death camps, but I am told that as many as 25% of the inmates died.
On detention camps in the United States currently, investigate these terms: Rex 84, Operation Garden Plot, and Conplan 2002. All sound like the overheated imaginings of conspiracy cranks, but are not.