HM Prison, Castlemaine was constructed of local sandstone between 1857 and 1861. It represents an important phase in the development of prison design associated with the completion of the Model Prison at Pentonville in 1842. The influence of the Pentonville plan is evident in the radial wings, central hall and exercise yard (industries building) of Castlemaine Gaol. Beechworth, Bendigo and Castlemaine were the most accurate representations in Victoria of Jebb's panopticon design.
The completion of the Castlemaine Gaol in 1861 represents an important phase of prison construction in Victoria. Between 1857 and 1864 a remarkable period of building activity saw eight prisons constructed on Pentonville principles in metropolitan and regional areas.
The HM Prison Castlemaine is an essentially intact example of a building type. The sequence of alterations, however, is of historical importance, representing the changing requirements of prison design and construction.
The H M Prison at Castlemaine is historically significant because of its ability to represent the size and status of this town which reached pre-eminence in the second half of the nineteenth century as a result of the discovery of gold.