Luis Monge, a convicted murderer, became the final person to be executed in Colorado's gas chamber on June 2, 1967. Monge was sentenced to death for the murder of two hitchhikers, a crime he was accused of committing in 1956. His execution drew national attention as it underscored the contentious debates surrounding the death penalty in the United States during this tumultuous period. Opposition to the gas chamber method of execution was growing, with many advocates arguing against the inhumanity of capital punishment itself.

Monge's case was marked by legal challenges and public outcry, as he maintained his innocence throughout the years. His execution was conducted amid a wave of protests from abolitionists who were against capital punishment. The execution proceeded in the gas chamber at the Colorado State Penitentiary, where Monge faced the lethal gas directly and was pronounced dead shortly after. This event not only concluded Monge's life but also marked a significant turning point in the American justice system's handling of the death penalty.

The last execution using this method occurred shortly before the landmark Supreme Court case Furman v. Georgia, which would declare the death penalty unconstitutional in its current form just a few years later. The controversy surrounding gas chamber executions, along with the ethical dilemmas inherent in capital punishment, shaped a changing national dialogue on the subject.