this is a map of all the concentration camps in Germany during World War II. When you manage to kill 6 million people and many more injured or imprisoned, then the infrastructure required is going to be vast.
The above is only for all the federal prisons.
Here’s another view of the prisons in USA from here.
To put these figures in context, we have slightly more jails and prisons in the U.S. -- 5,000 plus -- than we do degree-granting colleges and universities. In many parts of America, particularly the South, there are more people living in prisons than on college campuses.