What is "single-celling"

Single-celling is the practice of assigning only one inmate to each cell in a prison. John Howard has been credited as establishing the practice of single-celling in the United Kingdom and, by extension, in the United States. In 1957, only 15 prisons in the United States practiced single-celling exclusively while 41 prisons employed it with a portion of their cells and 44 housed multiple prisoners in all of their cells. Critics of single-celling suggest that the practice imposes psychologically harmful isolation on inmates, while advocates argue that single-celling alleviates many of the inmates' discomforts.