The American prison system is a massive organization - over two million Americans are currently incarcerated in this system. Aside from fines, community service, and capital punishment, it is our only method of punishing wrongdoers, and the use of incarceration heavily outweighs these punishments. This is the question that is not asked enough: is this the best way?
Public Punishment
Historically, most punishments were carried out in the full view of the public, often drawing crowds of hundreds and sometimes thousands to see the torture or execution of an enemy of the state or of the sovereign. These punishments, while gruesome and often excessive, served a very distinct purpose. As Michel Foucault puts it in Discipline and Punish, "The ceremony of the public torture and execution displayed for all to see the power relation that gave his force to the law" - in other words, the public punishment served as a visual and physical reminder of the power and legal significance of the ruler. These punishments were ended in the modern age because of their barbarity and inhumanity. But there were side effects.
Secret Punishment
Today, the system that exists stands nearly opposite to this. Hearings and trials are reasonably public, but the actual punishment, the incarceration, is carried out in private, behind high walls and barbed wire fences. The criminal - who has done a wrong to the whole of society in a Democratic country - is swept under the rug, removed from the sight of squeamish citizens. We do not like to acknowledge that we have crime, and society demands that we not see it, so our offenders are taken to where they cannot touch society or effect it. This limits the usefulness of the prison.
How to Punish Properly
To advocate a return to public, corporal punishment would be ridiculous and wrong, and that is certainly not the suggestion here. But imprisonment has a diminished and impotent effect on the populace, especially when it is kept secret and hidden from the view of the average citizen. Only half of the purpose of punishment is to punish the wrongdoer - the other half is designed to remind the potential criminal of the consequences of illegality. This current system does that weakly, if at all. What's more, all of our offenders are sent to the same place - murderers, rapists, burglars, people in possession of small amounts of drugs, etc. One critic of this system suggested that it was similar to a doctor prescribing the same remedy for all ills.
There are no easy answers, but it is time that the American people stop accepting incarceration as 'good enough'. It's clearly not. The volume of prisoners is a drain on the financial and moral resources of America, and it is time for a reassessment of means. Community service and work assignments should be used significantly more; violent offenders may need to be allotted their own institutions - and American children should be forced to visit prisons as a part of their civic education. At the very least, it must be asked whether or not these institutions serve the country as they are meant to.
Further Reading:
Michel Foucault, Discipline and Punish. 1977, Random House.