The total on June 30, 2005, was 56,428 more than at the same time in 2004, the government reported Sunday. That 2.6 percent increase from mid-2004 to mid-2005 translates into a weekly rise of 1,085 inmates.
Of particular note was the gain of 33,539 inmates in jails, the largest increase since 1997, researcher Allen J. Beck said. That was a 4.7 percent growth rate, compared with a 1.6 percent increase in people held in state and federal prisons.
Prisons accounted for about two-thirds of all inmates, or 1.4 million, while the other third, nearly 750,000, were in local jails, according to the Bureau of Justice Statistics.
Beck, the bureau's chief of corrections statistics, said the increase in the number of people in the 3,365 local jails is due partly to their changing role. Jails often hold inmates for state or federal systems, as well as people who have yet to begin serving a sentence.
"The jail population is increasingly unconvicted," Beck said. "Judges are perhaps more reluctant to release people pretrial."
The report by the Justice Department agency found that 62 percent of people in jails have not been convicted, meaning many of them are awaiting trial.
Overall, 738 people were locked up for every 100,000 residents, compared with a rate of 725 at mid-2004. The states with the highest rates were Louisiana and Georgia, with more than 1 percent of their populations in prison or jail. Rounding out the top five were Texas, Mississippi and Oklahoma.
The states with the lowest rates were Maine, Minnesota, Rhode Island, Vermont and New Hampshire.
Men were 10 times to 11 times more likely than women to be in prison or jail, but the number of women behind bars was growing at a faster rate, said Paige M. Harrison, the report's other author.
The racial makeup of inmates changed little in recent years, Beck said. In the 25-29 age group, an estimated 11.9 percent of black men were in prison or jails, compared with 3.9 percent of Hispanic males and 1.7 percent of white males.
Marc Mauer, executive director of The Sentencing Project, which supports alternatives to prison, said the incarceration rates for blacks were troubling.
"It's not a sign of a healthy community when we've come to use incarceration at such rates," he said.
Mauer also criticized sentencing guidelines, which he said remove judges' discretion, and said arrests for drug and parole violations swell prisons.
"If we want to see the prison population reduced, we need a much more comprehensive approach to sentencing and drug policy," he said.