Oklahoma, Mississippi and the Mountain states have set the pace in increasing the imprisonment of women, while several Northeastern states are curtailing the practice, according to a new report detailing sharp regional differences in the handling of female offenders.

The report, to be released Sunday by the New York-based Women's Prison Association, is touted as the most comprehensive state-by-state breakdown of the huge increase in incarceration of women over the past 30 years.

Overall, the number of female state inmates serving sentences of more than a year grew by 757 percent between 1977 and 2004, nearly twice the 388 percent increase for men, the report said.

Though the surge occurred nationwide, it was most notable in the Mountain states, where the number of incarcerated women soared by 1,600 percent, the report said.

According to federal statistics cited in the report, Colorado had 72 female inmates in 1977 and 1,900 in 2004, while the comparable numbers increased from 28 to 647 in Idaho, from two to 473 in Montana, from 187 to 2,545 in Arizona and from 30 to 502 in Utah.

Idaho, Wyoming and Montana were among six states, along with Oklahoma, North Dakota and Hawaii, where women comprised more than 10 percent of the prison population in 2004 — compared to the national average of 7 percent. In Rhode Island, by contrast, only 3.2 percent of the inmates were women.

Oklahoma had the highest per capita imprisonment rate for women — 129 behind bars for every 100,000 women in its population. Mississippi was second with a rate of 107. Women in those states were roughly 10 times more likely to be imprisoned than women in Massachusetts and Rhode Island, which shared the lowest rate of 11.

Nationwide, there were 1.42 million inmates in state and federal prisons at the end of 2004, including 96,125 women — up from 11,212 in 1977.

Though the overall surge of women behind bars has continued in recent years, it has tapered off in the Northeast, the report said. From 1999 to 2004, it said, the number of female inmates dropped by 23 percent in New York and 21 percent in New Jersey — part of broader reductions that also cut the number of male inmates.

The report concurred with previous analyses attributing much of the nationwide increase in women's imprisonment to the war on drugs. The proportion of women serving time for drug offenses has risen sharply in recent years, while the proportion convicted of serious violent crimes has dropped, it said.

Bob Anez, a Corrections Department spokesman in Montana, confirmed that drug offenses — especially related to methamphetamine — were a major factor in the high proportion of female inmates in the state. Half the women imprisoned from January through March had committed meth-related offenses, he said.

Jerry Massie of Oklahoma's Corrections Department also said rising drug convictions were a factor in the high number of imprisoned women, but he noted that Oklahoma has one of the highest incarceration rates for men as well as for women.

Ann Jacobs, executive director of the Women's Prison Association, said states with high rates of women behind bars should look closely at alternative sentencing, particularly mandatory treatment as an option for drug offenders.

"It's startling to think that Oklahoma incarcerates 129 of every 100,000 women, while other states can provide public safety by incarcerating 11 of every 100,000," she said. "Women in Oklahoma can't possibly be 10 times worse."

K.C. Moon, executive director of the Oklahoma Criminal Justice Resource Center, said the state's high incarceration rate is linked to the types of crimes that are felonies — including simple drug possession and relatively minor thefts.

"Those are two types of crimes that are typically committed by women," Moon said. "In Oklahoma, we choose to make lower-level crimes felonies, therefore we stand out like a sore thumb."

The Women's Prison Association and like-minded groups focus attention on female inmates in part because they are more likely than men to be primary caretakers of children, and their incarceration can place severe strains on families.

The report urged an expansion of research to identify factors that have contributed to the increase of female inmates and to develop policies which help at-risk women lead law-abiding, self-sufficient lives. Jacobs said the reduction of female inmates now occurring in some Northeast states would be worth celebrating only if coupled with investment in social programs that could reduce recidivism.