Question: When did the criminal gang formed by someone serving six life sentences at the ADX Florence supermax prison in Colorado?

Context paragraphs:
Wadih el-Hage: Wadih Elias el-Hage (Arabic: وديع الحاج‎ ‎ , "Wadī‘ al-Ḥāj") (born July 25, 1960) is a former al-Qaeda member who is serving life imprisonment in the United States for his part in the 1998 United States embassy bombings.  He was indicted and arrested in 1998, and convicted on all counts and sentenced to life without parole in 2001.  His sentence was overturned in 2008 because it was based on federal mandatory sentencing guidelines invalidated by the US Supreme Court in 2005.  He was re-sentenced to life without parole in 2013.  El-Hage and his co-defendants are currently in the supermax prison known as ADX Florence.

Larry Hoover: Larry Hoover (born November 30, 1950) is an American gang leader and founder of the Chicago street gang called the Gangster Disciples.  Hoover is currently serving six life sentences at the ADX Florence supermax prison in Florence, Colorado.  His sentences include a 150–200 year sentence for a 1973 murder; and in 1997 after a 17-year investigation of conspiracy, extortion, money laundering, and running a continuing criminal enterprise for leading the gang from state prison, he received a life sentence.

Forty Thieves (New York gang): The Forty Thieves — likely named after Ali Baba and the Forty Thieves — were formed in 1825 and alleged to be the first known and oldest New York City criminal street gang.  The Thieves consisted primarily of Irish immigrants, and Irish Americans who terrorized the Five Points neighborhood of 19th century Manhattan.  Another criminal gang named the "Forty Thieves" which had no criminal ties to the New York gang was formed in London, England in 1828.  From 1873-1950s, an all-female London criminal gang known as the "Forty Elephants" was also known to use the name the Forty Thieves.  Later a criminal gang in Philadelphia called themselves the Forty Thieves.  The Kerryonians another early Irish gang formed in the same year as the Forty Thieves were alleged to be the second oldest organized criminal gang in New York City.

Zacarias Moussaoui: Zacarias Moussaoui (Arabic: زكريا موسوي, "Zakariyyā Mūsawī "; born May 30, 1968) is a French citizen who pleaded guilty in U.S. federal court to conspiring to kill citizens of the United States as part of the September 11 attacks.  As a result of his conviction, he is serving six life sentences without parole at the Federal ADX Supermax prison in Florence, Colorado.

ADX Florence: The United States Penitentiary, Administrative Maximum Facility (ADX) is an American federal supermax prison for male inmates located in Fremont County, Colorado.  It is unofficially known as ADX Florence, Florence ADMAX, or the "Alcatraz of the Rockies."  It is part of the Florence Federal Correctional Complex, which is operated by the Federal Bureau of Prisons (BOP), a division of the United States Department of Justice.  It houses the male inmates in the federal prison system who are deemed the most dangerous and in need of the tightest control.  ADX also includes an adjacent minimum-security camp that, as of 2014 , houses more prisoners than the supermax unit.

Gangster Disciples: The Gangster Disciples are a criminal gang which was formed on the South-side of Chicago in the late 1960s, by Larry Hoover, leader of the High Life Supreme Gangsters, and David Barksdale, leader of the Black Disciples.  The two groups united to form the Black Gangster Disciple Nation (BGDN).  They later had disagreements, which led to the breakup of the gangs.

Michael Swango: Joseph Michael Swango (born October 21, 1954) is an American serial killer and a former physician.  It is estimated that Swango has been involved in as many as 60 fatal poisonings of patients and colleagues, though he only admitted to causing four deaths.  He was sentenced in 2000 to three consecutive life terms without the possibility of parole, and is serving that sentence at the ADX Florence supermax prison near Florence, Colorado.

United States Penitentiary, Florence High: The United States Penitentiary, Florence High (USP Florence High) is a high-security United States federal prison for male inmates in Colorado.  It is operated by the Federal Bureau of Prisons, a division of the United States Department of Justice.  USP Florence High is part of the Florence Federal Correctional Complex (FCC Florence), which is situated on 49 acres of land and houses different facilities with varying degrees of security.  It is named "Florence High" in order to differentiate it from the United States Penitentiary, Florence ADX, the federal supermax prison located in the same complex.

Robert Hanssen: Robert Philip Hanssen (born April 18, 1944) is a former Federal Bureau of Investigation (FBI) agent who spied for Soviet and Russian intelligence services against the United States for 22 years from 1979 to 2001.  He is currently serving 15 consecutive life sentences at ADX Florence, a federal supermax prison near Florence, Colorado.

Cunningham v. Federal Bureau of Prisons: Cunningham v. Federal Bureau of Prisons is a federal class-action lawsuit against the Federal Bureau of Prisons and officials who run ADX Florence, a supermax prison in Fremont County, Colorado.  In 2012, 11 inmates filed the suit, originally named Bacote v. Federal Bureau of Prisons.  The suit alleges chronic abuse, failure to properly diagnose, and neglect of prisoners who are seriously mentally ill.  As of March 2015 settlement negotiations were underway with the help of a federal magistrate and some improvements had been made by the Bureau of Prisons.

Supporting paragraphs: Gangster Disciples Larry Hoover
Answer: the late 1960s