Jail is not supposed to be where you put the mentally ill or those too poor to pay bail. Nor is it supposed to be where African Americans, Hispanics, Native Americans and Asians go for crimes that don’t land white people behind bars. But that is what they are increasingly becoming.

The primary purpose of jails, unlike prisons, is to be a temporary holding space where those who are a danger to the public or are a flight risk can await court proceedings. But they now hold many who are neither. Too often, jails are warehouses of low-risk individuals who are too poor to post bail or too sick for existing community resources to manage.

Many jails today are being asked to do the job of mental health institutions, even though they lack the resources and expertise to treat people suffering from mental illness or substance abuse. Research shows that serious mental illness affects an estimated 14.5% of men in jails and 31% of women - rates that are three to six times higher than in the general population.

Jail time is also being served by nonviolent offenders who can’t afford bail or a wide variety of criminal justice system fees, while wealthy defendants buy their way out. In New York City in 2012, 31% of non-felony defendants confined in jail until their cases were resolved were unable to make bail of less than $500. People are locked up – for months – as a result of driving with an expired license, or for a minor drug offense.

While incarceration starts locally in county and city jails, it of course doesn’t stop there. Research shows that even a few days in jail before trial or release can increase the likelihood of receiving a sentence of incarceration – and can increase the harshness of that sentence.

Unnecessary and inappropriate jail stays can cut off residents from their jobs, children and much-needed support like mental health counseling or drug treatment. It can send them into a downward spiral that can lead to serious crime, addiction, homelessness and future incarceration. This swells the prison population, contributing to our nation’s massive problem of over-incarceration.

This situation demands a change. There are plenty of practical solutions we can turn to that will strengthen public safety, reduce costs and restore fairness. So why not roll them out nationally?

In Portland, Oregon, the police department runs a mobile crisis unit that connects individuals with mental health services. It offers medical treatment instead of detention for people whose mental illnesses or substance abuse problems result in repeated encounters with law enforcement. These policies saved the county nearly $16 million between 2008 and 2010. Such initiatives are far too rare. We should implement such services in every county.

Similarly, the Hennepin County District Attorney’s office in Minnesota has kept more than 800 people out of jail by providing other pathways to justice. A new program replaces jail time for low-level offenders with community service and has directed more than $440,000 in restitution to victims. They achieved these incredible results by partnering with the nonprofit Operation de Novo to help low-risk arrestees make amends through community service and a payment plan.

These examples are representative of many other local reforms nationwide. Since jails are where our nation’s over-incarceration problem begins, we must encourage more local innovation across the country to make the criminal justice system fairer and more efficient by focusing on rehabilitation, not incarceration, for nonviolent offenders, applying programs proven to help reduce repeat offenses and saving tax dollars that can be better spent on other community needs. The MacArthur Foundation’s new Safety and Justice Challenge was formed to encourage these programs; we will be investing $75 million over five years to support innovation in local jurisdictions so that we can implement more of what’s working in Oregon and Minnesota.

We all have a stake in improving the way America thinks about and uses jails. Society is better off if people who do not deserve or need to be in jail do not end up there. Police officers, judges, prosecutors, defenders and corrections officers who handle overloaded dockets would see their load reduced. Unfair, ineffective and inefficient justice systems do not increase public safety or the well-being of individuals and their communities. They are inconsistent with American ideals.