There are several ways to eliminate prison overcrowding. One would be to devote more funds to building new prisons. This could be done through raising taxes or through reallocating current funds away from other projects, such as schools or roads, to prison construction.
However, as neither of the above proposals is likely to be politically viable, another alternative would be to reduce sentences for existing non-violent offenders and/or to rely more heavily on parole than incarceration. Decriminalizing certain offenses, such as being caught having small amounts of illegal substances, could also lower prison populations. Given that the United States incarcerates a high percentage of its total population compared to other nations, trying to cut the prison population could be a reasonable option that would gain popular support.
Since early childhood educaton programs have been shown to reduce criminal behavior when children grow up, a long-term solution to prison overcrowding could be investments in preschool programs. Fewer people committing crimes would reduce prison overcrowding.