Below is a list of prisons in Colorado that currently accept books sent to inmates from Unchained Books:
Colorado Territorial Correctional Facility (state)
Crowley County Correctional Facility (private)
Federal Correctional Institution at Florence (federal)
Federal Correctional Institution at Englewood (federal)
High Plains Correctional Facility (state)
Kit Carson Correctional Center (private)
La Vista Correctional Facility (state)
Rifle Correctional Center (state)
San Carlos Correctional Facility (state)
unchainedbooks.wordpress.com 
This is a great cause.
I was told by an inmate at Canon city that inmates may only posses two books of their own in their cells. What could be better than books for inmates?