Final answer:
The Quakers, particularly those in Pennsylvania, were key in advocating for prison reform and the shift towards incarceration with hard labor as primary criminal sanctions in the late 18th century.
Step-by-step explanation:
The group of colonial Americans instrumental in advocating for the use of incarceration alongside hard labor instead of corporal punishment was the Quakers. In the late 18th century, this religious community pushed for prison reform based on their principles of rehabilitation and moral redemption. The Quakers, particularly in Pennsylvania, believed in transforming criminals into law-abiding citizens through hard work, religious instruction, and isolation from societal vices.
This shift in penal policy was part of a broader movement of social reform that included not just prisons but also education and care for the mentally ill. Moreover, these reformers considered the harsh penalties such as public whipping or execution to be inhumane and ineffective. Their efforts led to significant changes in the criminal justice system, emphasizing rehabilitation over punitive measures.