Crime and punishment watcher Mara Leveritt alerts me to an interactive map that's worth noodling with if you have the time.
The Justice Atlas of Sentencing and Corrections allows you to look at any state, county or ZIP code
for the number and rate of people admitted and released from prison, probationers and parolees, along with the cost. The most recent data is from 2008, however.
In the map above of Pulaski County, the darker the shading the higher the prison admission rate in the various ZIP codes.