The phrase "large prisons" refers to prisons that are big in size or have a high capacity to hold a large number of people who have been convicted of crimes and sentenced to serve time in custody. Full definition
They want to end the use of large prison facilities. (nprillinois.org)
States with larger prison populations and more robust economies tend to pay higher salaries, such as New Jersey, California, New York, Massachusetts, and Rhode Island. (sokanu.com)
In California, with the nation's largest prison system, a federal district court found in 2005 that the parole board «operated under a sub rosa policy that all murderers [typically serving life terms] be found unsuitable for parole.» (religion-online.org)