I can't say that I've researched the history of crime and punishment over the centuries and how imprisonment fits into that. Though I was intending to refer to more recent history, somewhere from around the founding of America to the beginning of modern-era widespread policing.

If you've read anything on it, exactly what were they using for punishment then? Other things I've read of in various places include execution, the stocks, other forms of physical punishments. IIRC, some Islamic societies still recommend cutting the hands off of thieves. All of this stuff makes imprisonment seem rather sanitary and lenient by comparison.