In my last book, Boot Camp, I wrote about a secret prison system for teenagers in the United States. Teens do not have to be found guilty of a crime to be sent to one of these facilities, also known as boot camps. All they have to be is under the age of eighteen and have parents or guardians who want to send them away.

There is yet another system of detention in our country that holds not thousands, but millions, of innocent people against their wills. Unlike boot camps, which are often located in remote parts of the landscape, these social and economic gulags are hidden in plain sight, often in inner cities,...