This chapter considers the emergence of imprisonment as the predominant form of punishment for the majority offences from the mid-nineteenth century onwards in Britain. It examines imprisonment before and during the eighteenth century through to the Victorian period. During this time, the use and purpose of prisons changed from places of detention to institutions for transforming the character and behaviour of offenders. In addressing the change or transformation in the purpose of the prison, this chapter provides and overview of the key changes and developments that shaped the use of imprisonment and prison regimes between the late eighteenth and the mid-twentieth centuries. In particular, it addresses the period of prison 'reform' in the late eighteenth century, noting the influence of key figures such as John Howard and Elizabeth Fry, and outlines how the change in the purpose of prison has been interpreted by criminologists and historians. When examining developments from the beginning of the nineteenth century, the chapter considers the separate and silent systems of imprisonment, and the reformative potential that these systems were thought to offer. From the mid-nineteenth century, prison regimes became more severe and focused on long hours of hard labour and harsh living condition with the purpose of deterring prisoners from future offending. Following this, convict prisons were established to hold long-term prisoners, and local prisons came under government control in 1878. The final section of this chapter examines the changes in prison policy and practice, from the Gladstone Committee report in 1985, through the first half of the twentieth century until the Prison Act 1952. Throughout the chapter reference is made to other changes in punishment which affected the use and nature of imprisonment, particularly the decline in the use of execution and the transportation of offenders to America and later to Australasia. In examining prison history, it is important to remember that there is not just one 'history' of prisons and imprisonment, but rather there are different histories, accounts, and perspectives. These distinct interpretations are offered by prisoners, prison officials, 'reformers', chaplains, and social commentators who were writing at the time, and, latterly, by criminologists and historians, who look back at events and attempt to understand the histories and experiences of prison and imprisonment. Finally, although this chapter is concerned with the transformation of imprisonment between the end of the eighteenth and the mid-twentieth centuries, many of the issues raised are relevant when examining prisons and imprisonment in the twenty-first century.