SACRAMENTO, Calif. (AP) -- California prisons mark a milestone Friday, when officials announce they have removed the last of nearly 20,000 extra beds that had been jammed into gymnasiums and other common areas to house inmates who overflowed traditional prison cells.

Inmates in rows of double- and triple-stacked bunk beds became "the iconic symbol of California's prison overcrowding crisis," Corrections Secretary Matthew Cate said in announcing an end to what the Department of Corrections and Rehabilitation formally calls "nontraditional beds."

Crowding was so bad that it was hours before guards discovered that an inmate had been killed in his bunk in a makeshift dormitory at the California Rehabilitation Center in Riverside County in 2005, former state corrections secretary Jeanne Woodford told federal judges in 2008.

The judges have since forced California to radically change the way it punishes criminals. The prison population has dropped by nearly 19,000 inmates since a new law took effect in October that is sending less serious offenders to county jails instead of state prisons.

California currently has nearly 142,000 inmates but must shed another 17,000 inmates to reach the June 2103 court deadline to reduce crowding in its 33 adult prisons. The federal courts ordered the state to reduce its inmate population as a way to improve inmate medical care, which was so inadequate that judges ruled it violated prisoners' constitutional rights.

The nontraditional beds once held more inmates than the entire prison populations of 25 other states, according to national statistics for 2010, the most recent available.

The U.S. Supreme Court published two photographs of tattooed, shirtless inmates milling around three-tier bunk beds as part of its ruling last year upholding the authority of lower courts to order California to reduce crowding.

Cramped conditions promote unrest and violence, the justices said. The court's ruling cited a medical expert who testified that forcing large numbers of inmates to share a few toilets made the congested areas "breeding grounds for disease." The crowding was unhealthy and dangerous not only for inmates, the court said, but for the guards, as well. The ratio in some overcrowded dormitories was often two or three guards for every 200 inmates.

The use of the nontraditional beds dates back a quarter-century but spiked when California prisons filled to bursting as get-tough sentencing laws took effect. At their peak in August 2007, the department had 72 gyms and 125 dayrooms jammed with 19,618 inmate beds.

"They provided an accurate and extremely graphic example of the crowding and inhumanity that engulfed the entire system," said Don Specter, director of the nonprofit Prison Law Office in Berkeley, which sued to force the state to ease crowding as a way to improve the treatment of sick and mentally ill inmates.

Cate, the corrections secretary, scheduled a news conference Friday to mark the occasion at Deuel Vocational Institution in Tracy, 70 miles south of the state capital.

The prison lost its original purpose a decade ago when it was pressed into use as a reception center for newly arriving prisoners. At one point, more than 1,000 inmates were shoehorned into makeshift areas at the prison, crowding that prison officials say helped spark a riot in 2003 that injured nine inmates and one employee.

The institution once offered 13 vocational education programs, including painting, welding, office machine repair, shoe repair and electronics, which disappeared.

Now that there is more space for classrooms, officials said the prison is expected to again offer classes in welding, plumbing, heating and air conditioning, and auto body repair.

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