On 1 April 1995, HM Prisons Thorp Arch and Rudgate amalgamated to form HMP Wealstun. This was an historic development for the Prison Service, and had the effect of creating a category C (closed) side and category D (open) side within one establishment.. In 2008, the open prison closed and the prison underwent a conversion to provide additional category C places; the full prison commenced operation in May 2010.
There are 10 residential units, and an assessment and separation unit (segregation unit).
- Anderson (A) and Bell (B) units between them house 230 prisoners in a combination of single and double cells.
- Curie (C) unit houses 180 prisoners in single cells. It includes the first night centre, induction, safer cells and prisoners on the IDTS programme. It also includes the care suite..
- Darwin (D) unit is a single-cell accommodation unit, holding 120 prisoners.
- Eddison (E), Fry (F), Herschel (H), Ibsen (I) and Jenner (J) units hold just over 50 each in single cells. Ibsen house the induction unit for new prisoners
- A–D units all have their own exercise yards, accessed from within the units.