These prisons were built with the American Philadelphia system as a model, which amongst other things meant that common cells were replaced by individual cells where prisoners would be able to contemplate their fate.
Disse fængsler blev bygget med det amerikanske Philadelphiasystem som forebillede, hvilket blandt andet indebar at delte fængselsceller blev erstattet med enkeltceller, hvor fangerne skulle overveje deres skæbne.