Why is President Obama going to prison? It's not what you think.

President Obama is about to become the first sitting US president to see the inside of a prison.

On Thursday Mr. Obama will visit a medium-security prison for male offenders in Oklahoma, where he will meet with both law enforcement officials and non-violent drug offenders.

The historic visit comes as the president pushes forward on his agenda to reform the US criminal justice system, which by many accounts is has the largest population of prisoners in the world. The number of prisoners in the United States has swelled in recent decades from just 25,000 in 1980 to more than 214,000, largely due to strict mandatory sentences for drug offenses.

Criminal justice reform is one of the few political issues where politicians from both sides of the aisle are finding common ground. As the Montior's Amanda Paulson reports:

Several bipartisan bills designed to reduce mass incarceration have been gaining momentum in Congress, and sentencing reform has gotten support from an odd coalition of bedfellows, including the conservative Koch brothers, GOP presidential candidates like Sens. Ted Cruz of Texas and Rand Paul of Kentucky, the the American Civil Liberties Union, the National Association for the Advancement of Colored People, and liberal leaders in Congress. This week, it's President Obama’s turn to call for reform.

On Monday, Obama commuted the sentences of 46 nonviolent drug offenders because "their punishments did not fit the crime." On Tuesday, he further addressed the issue of what he sees as excessive punishment for nonviolent drug offenses in an address at an NAACP conference in Philadelphia.

“There are a lot of folks who belong in prison ... but over the last few decades, we’ve also locked up more and more nonviolent drug offenders than ever before, and that is the real reason our prison population is so high,” Obama told conference attendees.

“If you’re a low-level drug dealer or you violate parole, you owe some debt to society ... but you don’t owe 20 years, you don’t owe a life sentence. That’s disproportionate to the price that should be paid," he added.

Obama hopes that his visit will bring attention to mass incarceration and spur Congress to pass legislation aimed at prison reform.

This report includes material from the Associated Press.