Walnut Street Prison was a city jail and penitentiary house in Philadelphia, Pennsylvania, from 1790 to 1838.

This was made a new and permanent form of combating crime through the practice of solitary confinement, which was later adopted at the Eastern State Penitentiary.

Built within the courtyard of the existing structure, it included a series of small cells for individual prisoners.

Windows were high up (the cells had 9-foot-high (2.7 m) ceilings) and grated and louvered to prevent prisoners from looking onto the street.

Despite these difficulties, similar institutions were constructed at Newgate Prison in New York City in 1797 and in Trenton, New Jersey in 1798.