TAFT, Okla. — Julie Faircloth walked out of an Oklahoma prison near the head of a line of nearly 70 women who were freed on Monday, as part of one of the largest single-day releases of prisoners in the nation’s history.

They were greeted by screams of joy from relatives who had gathered outside the prison, a minimum-security facility southeast of Tulsa. Hugging first her mother, then her husband, Ms. Faircloth, 28, said she was overwhelmed. “I can’t even put words to it,” she said.

Across Oklahoma on Monday, 462 inmates doing time for drug possession or similar nonviolent crimes had their sentences commuted as the first step in an effort by state officials to shed the title of the nation’s incarceration capital.

“This is truly a blessing, to be able to get out on something like this, when you get overlooked so often,” said Ms. Faircloth, who plans to return to Willow, Okla., and hopes to attend college and score a job at a Hobby Lobby store.

As she and the other prisoners left the Dr. Eddie Warrior Correctional Center, they embraced relatives, some of whom they had not seen in months or years. Camera crews crowded around, recording a scene that would have been unfathomable in the state just a few years ago.

For more than a decade, legislators in several states have sought to send fewer nonviolent, low-level offenders to prison, in an effort to save money on incarceration and reserve resources for going after more serious criminals. Those efforts have occurred in states led by both Democrats and Republicans, including neighboring Texas.

But change has been slower to come to Oklahoma, which continues to vie with Louisiana for the highest per-capita imprisonment rate in the country.

Voters forced the hand of Oklahoma lawmakers in 2016 when, by a wide margin, they approved a plan to shrink prison rolls by downgrading many felonies to misdemeanors, including simple drug possession and minor property crimes.

The Legislature then approved a measure this year making that law retroactive and allowing the state’s pardon and parole board to more quickly review the sentences of many inmates whose crimes would no longer be considered felonies if they were charged today.

On Friday, the pardon and parole board recommended immediately commuting the sentences of 527 prisoners under that law, or about 2 percent of the state’s prison population of just under 26,000 inmates.

The governor, Kevin Stitt, ordered the commutations, and all but 65 of the 527 inmates walked out of prison on Monday; the remainder were being detained because of issues with their immigration status or because they face charges in other states, according to Oklahoma officials.

In addition to releasing the inmates sooner than expected, the state is taking other steps favored by criminal justice reform advocates to help the newly released prisoners with re-entry into society. Those include ensuring that inmates are released with a state-issued driver’s license or identification card, which are crucial for securing jobs, housing and other needs.

State officials said the prisoners being released had on average spent three years incarcerated, and were being let out an average of 1.34 years early. About three out of four are men. Officials also estimated that the release would save about $12 million in incarceration costs.

“This event is another mark on our historic timeline as we move the needle in criminal justice reform,” Governor Stitt said. He pledged to pursue other changes “that will offer our fellow citizens a second chance while also keeping our communities and streets safe.”

Advocates of reducing inmate populations across the country applauded the prisoner release but said Oklahoma remains behind many other states.

“This is a classic example of a state where voters on the right and the left agree on the need for criminal justice reform,” said Udi Ofer, the director of the justice division of the American Civil Liberties Union, which has been heavily involved in reform efforts in Oklahoma. “What’s happening today is an important step forward, but much more is needed.”

Mr. Ofer said the A.C.L.U. and other advocates will continue to push the State Legislature to pass other changes next year, including changes to laws that require some repeat offenses to automatically be subject to much harsher punishment, no matter the circumstances.

“Oklahoma will never substantially reduce its prison population until it tackles sentencing enhancements,” Mr. Ofer said.

Oklahoma officials said it was the largest single-day commutation of sentences the state had ever seen, and it was surely one of the largest in the nation’s history.

In 2003, Gov. George Ryan of Illinois commuted the sentences of 167 death-row prisoners to life sentences or less, just before he left office. And on Christmas in 1868, President Andrew Johnson granted pardons and amnesty for troops who had fought for the Confederacy during the Civil War, affecting hundreds of thousands of Southerners.

Andrew Speno, the state director of Oklahoma for Right on Crime, a group at the forefront of conservative efforts to reduce incarceration rates in the state, praised the commutations but said officials need to do much more.

“This is a very significant step, but it’s critical that it must not be the last step,” Mr. Speno said.

He also said the gains from Monday’s releases were at risk of being undermined by the state’s failure to use millions of dollars of savings, which have flowed from the 2016 referendum, to send more low-risk defendants to drug courts and other diversion programs and to fund mental-health services, job-placement help and other transition aids for newly released inmates.

“Our concern is that without the necessary community support, we could see these people back in the criminal justice system within six months,” Mr. Speno said. “This is a great move in the right direction, but if not done properly, it’s going to be counterproductive.”

At a ceremony at the prison in Taft to mark the releases, the governor’s wife, Sarah Stitt, emphasized that the state must embrace and support the former inmates.

“Oklahomans are ready to surround you and have a successful life in this state,” Mrs. Stitt said, adding that nearly 30 fairs were held inside prisons before the commutation day to help the inmates plan their transition.

One newly released inmate in Taft, Tina Martin, 32, said she had been facing seven more years in prison.

“It means the world to me because I could have done a lot of time,” Ms. Martin said before ticking off her plan of action: sober living, finishing cosmetology school and moving to Grove, Okla., with her family.

“It was God that got me here, and the governor,” she added.

Kristi Eaton reported from Taft, and Richard A. Oppel Jr. from New York.