Nothing new here. But it's good to have a refresher course every now and then. It's too easy for prisoners to be out of sight and out of mind.
(plus these are the neatest diagrams I've found in the subject)
Now it's 2,300,000 behind bars.
The increase is all since 1970 and the war on drugs.
It has little relationship to the crime rate. This is important. Because people generally don't have a problem with locking up criminals because there's more crime. We're just locking up more people. And the crime rate doesn't change because of it.
The incarceration rate is going still going up. Now it's above 750.
You can read the complete Justice Policy Institute report here. It's from 2000, but the later reports don't have the pretty diagrams. The latest report, Prisons in 2007, can be found here.