Final answer:
During the Progressive Era, rehabilitation was adopted as it connected with psychological and sociological theories, focusing on improving social conditions and reforming individuals.
Step-by-step explanation:
Rehabilitation was a popular philosophy during the Progressive Era, and it was closely tied to the acceptance of psychological and sociological theories of crime and delinquency. During this time, reformers aimed to improve the conditions contributing to vice and deviance in urban environments. They believed in changing the prison system to rehabilitate criminals rather than simply punish them. The theories of the time suggested that crime was a product of social factors rather than inherent traits, and through reform and education, individuals could be brought back into productive citizenship.