PORTLAND – U.S. corrections officials and policy experts who met at the first national conference on female prisoners in 1983 in Minnesota could have hardly anticipated how incarceration rates would explode over the next 20 years.

There were more than five times as many female inmates in 2002 than two decades earlier, according to the federal Bureau of Justice Statistics. That population boom provides the backdrop for the 10th National Workshop on Adult and Juvenile Female Offenders, which opens Saturday in Portland.

Denise Lord, associate commissioner of the Maine Department of Corrections, which is co-sponsoring the five-day conference, said the number of female inmates nearly doubled since the end of 2001 in Maine.

“Just in one year, the last year, it increased by more than 50 percent,” she said.

Nationally there were fewer than 18,000 female prisoners under federal and state jurisdiction in 1982 and more than 97,000 by the end of last year. The numbers of male prisoners skyrocketed as well. Still, the percentage of all prisoners who were women rose from 4.3 percent to 6.8 percent during the 20-year span.

Experts attribute the large increase to a variety of factors, including gender-blind sentencing, the closings of mental health facilities, and drug abuse. But Meda Chesney-Lind, a University of Hawaii researcher who’s scheduled to give the conference’s keynote address on Monday, said the biggest cause is harsher drug sentencing.

“That’s been a shift that’s occurred without a large conversation in the country,” she said. “It’s not just the Bush administration that didn’t want to talk about it. The Clinton administration didn’t want to talk about it.”

The increase in female inmates has sparked concern in Maine, and state officials hope to learn more about issues like gender responsiveness and juvenile incarceration from some of the fields top researchers.

The conference in Portland is expected to attract more than 500 researchers and criminal justice workers from around the country. It’s a mix of feminist professors and corrections officials that may seem odd, but participants say they all share an interest in helping women get back on their feet.

“Every two years you get quite a diverse group of women who come together who really have similar passions,” said Stephanie Covington of the Center for Gender & Justice in La Jolla, Calif.

Chesney-Lind added: “Many of us are now close personal friends with each other, so its not a phony, strained relationship.”

Attendees will participate in workshops, screen films and tour the new 70-bed womens unit at the Maine Correctional Center in Windham. Theyll be welcomed on Monday by Chief Justice Leigh Saufley of the Maine Supreme Judicial Court.