What follows is a more accurate history of the genre than you will find on the Wiki site. I'll continue to edit this page as I watch more films.

Condemned WomenMost women-in-prison films employ the same stock characters and formulaic situations which have since become cinematic cliches.

They generally begin with an innocent girl (the new fish) being wrongfully sent to a corrupt penitentiary or reform school run by a brutal and lecherous male or lesbian warden who might also be running an inmate prostitution ring on the side.

After the obligatory strip search, group shower, lesbian sex scenes, cat fights with a tough "queen bee" gang leader, a stabbing or two, cruel punishments and sexual assaults by sadistic guards and a yard riot quelled by spraying the prisoners with a firehose, the story usually concludes with a bloody uprising or escape sequence in which the villains meet with a grisly death. What more could any red blooded beer drinking male ask for?
House of Women
Women-in-prison films developed in the 1930s as melodramas in which young heroines were shown the way to a righteous life by way of the prison. It was not until the 1950s, beginning with the release of Caged (1950), starring Eleanor Parker and Agnes Moorehead, So Young, So Bad (also 1950), and Women's Prison (1955) with Ida Lupino and Cleo Moore that the modern expoitation elements began to surface.

99 WomenThe film that kicked the genre into full blown exploitation was Spanish directorJesus Franco's 99 Women (1969). His name would become synonymous with W.I.P. films directing such titles as Lover's of Devil's Island (1974), Barbed Wire Dolls (1975), Women Behind Bars (1975),Women in Cell Block 9 (1977), Ilsa, The Wicked Warden (1977), Love Camp (1977) , and Sadomania (1980).

The Big Doll HouseJack Hill's 1971 film The Big Doll House set off an explosion of money making Women in Prison product for the grindhouse and drive-in market in the United States. The majority of these were filmed in the Philippines where production costs were low. These steamy, "tropical hell-hole" variants were set in fictional Banana republic nations run by corrupt dictators in either South America or Southeast Asia. Here, a group of nubile prisoners, wearing the regulation halter tops and cutoffs, are herded together in a stockade prison camp and used as slave labour, such as cutting sugar cane or digging in a quarry. The harsher, isolated setting allows for scenes of unrestrained brutality with whip-cracking guards, diabolical punishments, and death by gruesome accident or execution. These films usually involve a revolution subplot with political prisoners freed by their comrades in a climactic raid where the evil warden and guards are shot and the camp is burned down. Producer Roger Corman gave his secretary Pam Grier her first role in The Big Doll House. She would go on to make several Filipino jungle films such as The Big Bird Cage, Women in Cages, and Black Mama, White Mama (story co-written by Jonathan Demme who would direct the influential Caged Heat).

Caged WomenItalian exploitation directors have produced scores of WiP films with far more graphic sex and violence than those produced in the U.S. Some examples include Bruno Mattei's Women's Prison Massacre (1985), Violence in a Women's Prison(1984), and Jail — A Women's Hell (2006), Edoardo Mulargia's Escape from Hell and Hotel Paradise (both 1980) and Sergio Garrone's Hell Behind Bars and Hell Penitentiary (both 1983). The Italians couldn't top Brazillian sleaze genius Oswaldo de Oliveira who directed Presídio de Mulheres Violentadas (1977), Bare Behind Bars (1980) and Amazon Jail (1982). His films pushed the envelope often crossing the line into pornography. Since Oliveria's films were often funded by Italian producers and had theatrical success in Italy, he like Jess Franco is often mistaken as an Italian director.

Ilsa She Wolf of the SSIn 1969 Lee Frost and Bob Cresse's Love Camp 7 was one of the first exploitation films that influenced the women in prison subgenre of Naziploitation. This sicker variation centers on the same theme of captive women suffering abuses in war-time prison camps. Partly inspired by the financial success of the U.S./Canadian Ilsa series and the Tinto Brass film Salon Kitty, Mattei, Garrone and other directors created scores of these films in the 1970s such as SS Experiment Love Camp, SS Camp 5: Women’s Hell, SS Extermination Camp, Gestapo's Last Orgy, Helga, She Wolf of Spilberg, SS Hell Camp, SS Girls, and Nazi Love Camp 27. It didn't take long before the subgenre was exhausted and died along with other Italian quick buck shenanigans such as Nunsploitation and Caligula films.

Meiko KajiIn Japan, prison films are often made into a series based on popular characters from manga comics such as Prisoner Maria and the Sasori (Scorpion) series which includes Female Convict 701: Scorpion (1972) starring Meiko Kaji. The Sasori series spawned over 10 films and several rival studio variations. Many of the Japanese W.I.P. films include themes of vengeance and retribution with a heroine who eventually becomes an avenging angel pursuing the drug or prostitution crime syndicate responsible for putting her behind bars.

Bamboo House of DollsThe abuse of Chinese women in Japanese detention or prisoner-of-war camps during World War II is depicted in a series of Hong Kong films. Prime examples include Bamboo House of Dolls (1972), and Excessive Torture in a Female Prison Camp (1983). Comfort Women (1992) is based on real events. Chinese prostitutes are abducted by Japanese soldiers and used for brutal scientific experiments at the notorious Unit 731 medical camp. A Chinese Torture Chamber Story (1994) and its sequel are based on historical records of China's Sung Dynasty.

Typical lurid VHS box from the 1980sThe Women In Prison film boom of the seventies began to fizzle out in the United States after the theatrical release of Tom DeSeimone's Reform School Girls (1985) but the genre remained popular on home video. Many films were badly transferred and re-released on VHS under different volumes such as Hellfire & Ice, Captive Women and the Women's Penitentiary Series by MCM Entertainment.

With the exception of straight to video films by Henri Charr the genre had pretty much died in the United States in the 90s. Cable televison programming geared towards women eventually turned the Women in Prison film back into the melodramas they once were.

In recent years, North American Pictures, the Canadian makers of Chained Heat 2 set up a separate production company in the Czech Republic called Bound Heat Films for creating R-rated, erotic WiP, Nazisploitation, and female slavery films. Many of these star Rena Riffel (from Showgirls). The ever reliable Japanese have continued to output Sasori films and are currently experiencing a J-Vid boom of genre features.